Winter Strategy

I am on Octopus Flux with a low tariff at 0200-0500 and high tariff 1600-1900. I am wondering if I set an import time from 0200-1600 might be feasible.

Assuming my day starts at 1600 with my battery at 100% this will carry me through to 0200. At 0200 I will import sufficient energy to charge to 100% (or whatever). During the day my home will draw from the battery and import from the grid to maintain that charge. From 1600 I will once again be depleting the battery.

On those days when I do have solar, for instance right now with no Sun forecast and actually have weak Sun and PV of 1.5kW the surplus will be exported. Should I still have Solar after 1600 (unlikely) the excess would continue to be exported.

I am sure wiser heads will spot problems, what is wrong with that strategy?

Roy124 I am on Octopus Flux

Perhaps reconsider that for the winter ?

How does your battery compare to typical daytime winter usage ? Assuming no solar, can you run for a day on battery alone ? And how much can you load-shift to overnight (washing machine, dishwasher, ...) For example, in my region E7 has a cheaper and longer overnight rate than Flux, so if filling your battery overnight gets you through the whole day, it's probably better ?

But maybe Octopus no longer have the best tariffs ? Eon Next Drive and Tomato lifestyle seem to be better, on paper, if you don't have EV or heat pump (and possibly also if you do). Tomato doesn't (currently) pay for export, so not great for summer, and you probably don't want to switch energy company every 6 months.

The last few days I have had some solar input and also used a 1400-1600 boost before the high tariff. My battery has then been sufficient to carry me through to 0200 and the cheap boost. In other words our usage exceeds the ability of our 5kW battery.

We don't have E7 and switching supplier is really too soon as I only joined Octopus after my Ovo handcuffs were removed. Ovo £150 switching penalty, even to the last 7 weeks, was punitive. I like the freedom with Octopus but shall look at Eon for the future.

I do load shift with washing machine and dishwasher at the low rate. We are in the process of getting an ASHP from Octopus at a very inexpensive price which is less than a third the price from other suppliers.

So will try over the next few days and see how it goes.

It is worthwhile looking at thus thread which has some useful advice:
https://community.givenergy.cloud/d/4930-winter-strategies

Rob

Rob, I had looked at that before. While guessing how much I need to top up before 1600hrs I had a think about over charging and want to see if maintaining the battery throughout the day is no more expensive than a limited up up before 1600.

Yesterday, with little Sun and only the 2hr boost charge I paid £1.25 (15p/kW) and 2p for export, happy with that. Today, with solar that was not forecast I didn't try for the 1400-1600 top up.

Roy124 We don't have E7

You should be able to get E7 if your smartmeter is reporting half-hourly usage. Doesn't need a special meter.

2x 5.2KWh batteries, 6.8KWp array, 15KWh typical daily use

From now until March many days will not fill the battery so

I am on Octopus Agile which generally has 2 three hours periods in each day in which the price is the lowest. I use WonderWatt, which calculates what charge level you need to get through the next 24 hours based on your usage and the expected solar so, when the Agile prices are not very good, I have set 2 smart charge periods each day. The afternoon charge period (1-4pm) is pretty good at getting past the following morning peak before any solar cuts in and that the early morning charge period (2-5am) is allowing for some fine adjustment if I have used more (or less) energy than the prediction or that the solar yield for the following day changes significantly. I also like the fact that the charge current is adjusted down for each period which is much kinder to the batteries.

So far it is working very well and the two charge schedules are allowing for the higher overnight usage when the dehumidifiers are running flat out (as they are at the moment as the humidity is so high in Bedfordshire having just had 160mm of rain in the last 2 days!)

This is now the set and forget setting I will use over the winter unless I get notified of Agile plunge pricing where I will enable the Agile charge windows appropriately.

This strategy might still work well with Flux and its single lower charge period and Cosy with three.

Pretty poor generation the last couple of days, and what I expect to see in October, November & December. My Solar was only fitted in Feb of this year so this is just a hunch

The battery died just after 19:00 so was pulling from the grid until the cheap rate at midnight, cooking and dryer was on in the evening (needs must with a family)

Fortunately, solar generation has been better today, and thankfully have battery reserves to see us through the evening.

Gen1 Hy5.0, 27 panels, 9.5 kwh battery in Pennies
Currently on Flux import and Flux export - which has been good since April with plenty of sun.
About 6kwh generation today ( clear skies no rain), but now there will be few days to do significant export.
I will go back to Eco 7 for a 7hr cheap night and charge slot to be fully charged by 07:00. Gen1 2.6kw limitation
Any solar will be beneficial through the day to keep as much charge in battery as possible.
Have to be on fixed 15p export , but that is OK as there is unlikely to be much export for six months.

Roy124 I am on Octopus Flux with a low tariff at 0200-0500 and high tariff 1600-1900. I am wondering if I set an import time from 0200-1600 might be feasible.

I posed this question last week and put it to the test today. I started with a fully charged battery in the Flux low tariff. Later this morning I set a new start time with a 1430 stop time. As expected the battery was recharged back to 100%. Now, despite cloud cover I was getting a 20% input from solar with the balance made up from the grid. The battery remained at 100% with no input to the home. In this it behaved just like IOF; an input at cheap rate to 100% with solar and grid feeding the home. If I wished to export I could set up a discharge period between 1600-1900. So far very similar to IOF.

Unlike IOF I would have to time the export so that I retain enough battery to last until after 1900. The difference with using Flux from 0200-1600 means I don't get any solar to the home and have to set my own export period. I conclude that the 0200-1600 is not efficient.

For the rest of October I shall see how it goes with 0200-0500 charge and a 1400-1600 top up as required. When there is little solar IOF will probably be much easier than manual Flux as the import and export will be automatic.

From mid-November it will be academic as we will switch to Cosy.

Roy124 For the rest of October I shall see how it goes with 0200-0500 charge and a 1400-1600 top up as required.

Would the 1400-1600 top-up be to 100% ? If so, that sounds worse than simply holding the charge until 1600. Eg suppose during the day you consume 5kWh from the battery. You now have to import 5kWh from the grid to get back up to 100%, so the net effect is the same as if you had just imported the 5kWh directly. Except that you've also incurred round-trip losses on the battery.

However, that is ignoring any solar contribution: holding the battery full means that if any solar exceeds consumption, it has to be exported, which is not ideal. So you do want to have some room in the battery to accept any excess solar around noon, or whenever peak solar is for you.

I wonder if some sort of hybrid model would be best - use the battery from 0500 until, say, 1000, then hold charge until 1600. Then top-up from grid from 1400 to 1600 as before. This should create some space in the battery for excess solar, but you avoid some of the round-trip loss for discharging then recharging the battery.

But you know your consumption habits best, so this might not work for you.

@DD I see what you mean. What I actually do is top the battery to 100% in the 0200-0500 period. This morning it reached 100% at 0330. The grid then supplied the home until 0500 when the charge period ended. This was fine as the energy in the battery was at 14p and so the power from the grid was also 14p. From 0500 the battery fed the home.

Normally, the battery and panels will supply the home but the battery will be well depleted come 1600 and would run out by 1900, therefore I routinely top up to 100% between 1500-1600. That 100% charge, without solar after 1600 will be depleted before the 0200 cheap rate.

"If so, that sounds worse than simply holding the charge until 1600. Eg suppose during the day you consume 5kWh from the battery. You now have to import 5kWh from the grid to get back up to 100%, so the net effect is the same as if you had just imported the 5kWh directly"

Mmm, that sounds like my 0200-1600 charge. Charge stops at 1600 and battery runs till 0200 when it will have some residual capacity, say 30%, which will be replaced at 14p. So I will persevere with my 0200-1600 regime. Thanks

Roy124 Mmm, that sounds like my 0200-1600 charge. Charge stops at 1600 and battery runs till 0200 when it will have some residual capacity, say 30%, which will be replaced at 14p. So I will persevere with my 0200-1600 regime.

Not quite - an 0200-1600 charge is largely equivalent to holding charge until 1600, but that means there's nowhere for excess solar to go (except export). Charging to only 80% means missing out on cheap-rate power. So I'm suggesting charging to 100% overnight, then running down slightly, then holding charge until 1400 when you top up.

Next question, of course, is how to implement such a thing. Gen-3 inverters probably have enough features to do it automatically (multiple charging slots and a pause timer), but I think you're gen-1 ? Might be more than wonderwatt can do, so might have to use the API scripts to do it. I have some scripts you're welcome to share - just need a raspberry pi or similar.

I think you said Octopus are installing you a heat pump soon - could always ask them if they'll allow you onto the cosy tariff early ;-)

DD I think you said Octopus are installing you a heat pump soon - could always ask them if they'll allow you onto the cosy tariff early ;-)

Now that is an idea. No harm in asking, don't want. don't ask; don't get.

I will play around on the GE App. Bit annoying today. It would not stop charging and switching to battery at 1600 and would not export at 1800. Similar to what I had before. Probably sort itself out toorrow.

I've just jumped from IOF to COSY today (I have aircon.....), We'll see how it goes, I'm using smart tariff beta card to charge in the low points.
It will take a day or two for all the battery levels to settle after IOF to get a picture of use.
I will keep an eye on Agile too...

Roy124 and tomorrow:

The 0200-0500 charge worked well. I was later setting a 1400-1600 boost. I tried with 10 minutes to run for a 1500-1600 boost but no joy. Somewhere the system - Givenergy Invertor or Octopus need rather more than a few minutes notice to change.

PS
It is more complicated than I thought. The Givenergy App Peak Power display shows the Charge started at 1415 whereas I know it was set for 1515. At 1645 my phone the Home display on the App shows the battery battery was still although the set time on the App to stop charge at 1600. Charge stopped at 1700 phone time.

There is clearly a miss match between my phone on BST and the Givenergy settings. Does 1500 on my App display equate to 1500 in Octopus?

Very confused.

I have just tried to follow the thread of 2 years ago, still confused.

Phone time 0200, Givenergy App* time 0100, What is the Octopus time?

If App time is the same as Octopus time then no issues.

*I assume the App time from the graphs is also Inverter time.

Roy124 There is clearly a miss match between my phone on BST and the Givenergy settings. Does 1500 on my App display equate to 1500 in Octopus?

In the remote-control page on the portal, there's a button to set the inverter's time and date. Embedded systems are often set to always run in UTC, but givenergy seem to automatically update time every time the clock changes, so we have to assume the inverter is intended to run on local time.

The third-party app https://givenergymonitor.wixsite.com/tutorials is able to show the inverter time.

Not sure what you mean by Octopus time. AFAIK Octopus tariffs always follow local time, so during BST, 0200 to 0500 corresponds to 0100 to 0400 UTC. But then when the clocks change, the tariff will change to UTC 0200 to 0500.

DD Not sure what you mean by Octopus time. AFAIK Octopus tariffs always follow local time, so during BST, 0200 to 0500 corresponds to 0100 to 0400 UTC. But then when the clocks change, the tariff will change to UTC 0200 to 0500.

That is exactly what I was hoping.

Now I have to resolve the issue between the time on my phone (1700), the setting in the App (1600) and inverter time.

I found the page on the Portal:

General Inverter Battery Charge/Discharge Schedules

then this:

Inverter
Time & Date Control
Time & Date
​

Set Date and Time

But there is no apparent way of setting or even seeing what times it means. I clicked SEND and was told it was written successfully, but what was written as I could make no entry and it displayed no date or time.

Should I set the App charge times to 0100-0400 to match the Octopus schedule of 0200-0500?

Roy124 yes, it's annoying that you can't choose what to send. That's why I suggested the alternative android app. (Or if you use iOS there is another app you can use.)

(Does it say in the activity log at the bottom what values it actually sent ?)

I am using the Android App. The activity log shows correctly what I set, it was 1600 for the Stop Charge time (as per Octopus) and the new 0400 sent and received on the assumption that it will be the 0500 BST used by Octopus.

Hopefully all will be clear at the end of the month but it would be better if I knew what Givenergy used UTC or BST. It certainly looks like UTC.

Roy124 Hopefully all will be clear at the end of the month but it would be better if I knew what Givenergy used UTC or BST. It certainly looks like UTC.

The inverter uses local time, so UTC or BST as appropriate and as @DD says there's a scheduled job that GivEnergy run that changes the inverter times when the clocks change.

Octopus pricing also works on local time all the time, so you shouldn't ever have to worry about changing the clocks in your schedules.

On my (iPad OS) app, the peak import shows between 04:30-05:00, on my Home Assistant I can see the peak import was at 04:40, so it matches. If you are seeing wrong data in the app then I'd put money on the app being wrong

Roy124 Should I set the App charge times to 0100-0400 to match the Octopus schedule of 0200-0500?

No because all times are in local time. Set the charge times to 0200-0500.

@geoffreycoan ah, but why, with the App set to 1500-1600 does the energy dynamic flow graph show flow from 1600-1700? When I look at the Power Graph and the start time and stop time are the set times. Then, looking at the first daily power spike it shows at 0615 when it was actually at 0715.

This strongly suggests that the graph is based on UTC not BST.

Roy124 Here’s my counter evidence:

App showing current data up to now, the graph ends at 22:00, same as the clock on my ipad:

Power graph from today in the app, shows the peak electricity generation was at 10:40:

And corresponding graph from Home Assistant showing the same solar generation peak:

I can’t explain why you see everything shifted out by 1 hour when I don’t, my only guess is that its something to do with the date/time settings on the device you are using, maybe its set to UTC not local time, or localisation on the device is wrong. I don’t know, but everything I see and all the control of the inverters that I have been doing for the last year is all corresponding to local time.

Alternative thought, the time zone on your inverter is set wrongly? I think you have to set it to UTC in the portal regardless of whether we are in BST or not before you sync the time.

Just done a further check and the battery data on the computer is logged one hour earlier, ie UTC. The question now is how to find the inverter time zone setting.

Roy124 there's nothing to suggest the inverter has a timezone - just a clock that is adjusted every time bst starts and ends.

geoffreycoan Alternative thought, the time zone on your inverter is set wrongly? I think you have to set it to UTC in the portal regardless of whether we are in BST or not before you sync the time.

Sorry to clarify, I didn't write that bit clearly. As @DD says, there is no visible sign that the inverter has any concept of time zone, it just has a 'current time' that you can sync from the GivEnergy portal and the portal takes care of adjusting the inverter time when the clocks change between UTC and BST,

In account settings you have the ability to set the timezone for your account:

The only clock option you have under account settings section of the portal is to sync the inverter with the portal time - I believe this uses the timezone for your account:

There is also in the remote control section of the portal which is I think is the same control setting:

@Roy124 Suggest you check your account timezone, if necessary change it to the same as mine and sync the inverter clock from the portal

geoffreycoan @Roy124 Suggest you check your account timezone, if necessary change it to the same as mine and sync the inverter clock from the portal

Spot on.

I actually found the time zone setting in My Account just before I read your comment. There are lots of UTC options and I had had hit Azores, possibly because I set it when we were on UTC and made the assumption that they would go plus 1 come summer.

Thanks for persevering with your advice.

Roy124 🎉

DD Tomato lifestyle seem to be better, on paper

I switched to Tomato Lifestyle EV (rate comparison here) end of last month. Customer service non-existent. Have tried emailing (no answer), tweeting (no answer) and calling (after being on hold for 10 minutes or so they drop the line)

Their customer facing dashboard is via sister company myWatts.co.uk - which for the first few days bears ZERO resemblance to my actual grid usage (did they make it up? have they linked the wrong meter?)

Not a great experience so far, and I'm beginning to wonder whether I should grin and bear it for the cheap rates, or switch back to Octopus Go using the 14 day cooling off period.

26Left You have to ask?

Octopus actually has UK based answer services too.

Roy124 Octopus have offshored part of their call centre capacity to South Africa - nothing like as good as it was unfortunately.

After the fifth attempt I got through to Tomato. Took a while to explain why I thought their readings were wrong, to find my email etc. It's been referred to a dev team - apparently I should hear back next week...

Hello. We are on Octopus Flux. We have a Gen 2 5kW hybrid inverter, 2x 9.5kW batteries, and 9kW PV arrays (5.2kW facing SE, and 3.8kW facing NW). In winter, we use about 38kW of power a day, double what our batteries can store.

During winter, we:
02:00-05:00 import from grid. Three hours is enough to add 50% charge, or 9.5kW.
05:05-15:55 'Pause Discharge' the battery [via the web portal - Remote Control section], meaning we run off the mains at day rate, supplemented by whatever PV can be generated, and excess PV goes to the battery. This ensures we get to 16:00 with at least 54% in the battery, enough to last us through until after 19:00.
16:00-19:00 Run off the battery, and export to the grid down to 50% SOC if by some miracle we have much more than that.
19:00-02:00 Run off the battery until it goes flat, then use the mains at standard rate.

Am contemplating moving to Agile, but it's so hands-on that I'll probably stay on Flux.

miffy Not as much capacity as you, like Gen 1, 5,25 kW Inverter, 1 5kW battery and 3.25kW array. At the moment (with Gas) we max at 15/16kW/day. Your battery/net routing is exactly what I was considering. The only doubt I had was not using the battery during the day - psychological really.

Following a tip here I tried MyEnergyOptimiser.co.uk the best thing is the tech support by Richard the owner who has set the program up based on my best guesses at demand and consumption. So far the App/Program looks simple enough with a free option to get you going.

miffy Am contemplating moving to Agile, but it's so hands-on that I'll probably stay on Flux.

Just out of interest, did you look into intelligent flux ?

miffy My setup is just a bit smaller than yours - 7.4kW PV / 5.0 HY Gen3 / 2x 9.5kW bat and daily usage is about 12-14kWh.

I am contemplating going onto IOG as I have an EV and do charge occasionally, but mostly because it gives me longer, lower cost night charging. A potential alternative is to switch to Economy 7, which will gives an extra 3-4 hours night time charging, enabling a full charge with shorter night-time grid float after. I would suggest you consider those options also.

I presume you've rejected getting a larger battery or adding a second inverter to increase the battery charge rate, or both. That seems to be the biggest issue you have (not being able to charge up to 90+% overnight)?

PS I looked at Oct Agile too, but concluded it was likely to increase my costs! Be careful!

DD Yes, I looked at IF and decided against it because:
a. During winter, it isn't the best tariff. Other people who have done the heavy lifting with regards to the maths say IF is only worth it if you generate a lot more than you use, therefore May-Sept for most people.
b. If your solar array is larger than the inverter capacity, which ours is, IF has no ability to account for that, and capping of generation will occur if there is no or little space in the battery. In summer, I have to ensure our battery does not get much above 90% until 15:00 else any generation above 5.3kW will get capped. [Capping occurs when the PV generates more kW than the inverter can handle. The max the inverter can do is 5kW for the inverter/house/export and 3.6kW to the battery, so 8.5kW, however when the battery is at over 90% charge, the charge rate drops.]
c. I don't want to hand control of my battery to Octopus. I want to control it myself, thanks. The paltry amount extra they'll pay me compared to normal Flux isn't worth it. And, I don't trust them to use the battery in a way to best benefit me.

We don't have an EV, so Octopus Go isn't an option. I'm shit at Home Assistant, so if we had another inverter installed for a 'plant' system, I wouldn't know how to set it up to avoid cross-charging. This has been on my radar as a possibility though.

miffy a. During winter, it isn't the best tariff. Other people who have done the heavy lifting with regards to the maths say IF is only worth it if you generate a lot more than you use, therefore May-Sept for most people.

Arguably the same is true if Flux ?

But I also rejected it primarily on not being certain exactly how octopus would actually use the battery. And I guess as we go into savings-sessions season, we want to control timing ourselves.

I ran IoF this summer May to Sept 30th.
IOF have full control
They drained battery to ₁₈-20% each day between 16:00-19:00
Charged mostly overnight in 1hr blocks,
Occasional 1hr discharge in the early hrs (05:00 ish)
Seemed to leave 10% free battery space if the day was going to be sunny to allow clipping charge.
Turned ECO all the time. (the grid's your battery...)
Worked out about 25% more profitable than other tariffs for me.

I used Intelligent Flux over summer but have changed to agile for over winter using predbat. I think I'll go back to IF in April/May again. One advantage of intelligent Flux is that I'm not looking at Home Assistant every hour..........

We have changed to Intelligent Flux fron Flux as I was fed up having to check all day what was happening with Flux now winter is here. However it looks like that was a mistake as battery never gets above 80% even today which has been sunny all day. We have a booster for hot water so that when battery reaches 100%, which I expected today, it heats our water cylinder. So now I am unsure whether to give it more time and use the booster manually and see what it costs ir go back to Flux.
Anybody had this problem?

Lynn However it looks like that was a mistake as battery never gets above 80%

Does that matter? You can treat the grid as a virtual lossless battery (can export then re-import any amount for zero net cost). The thing that matters is whether battery can get you through the expensive peak rate.

Not really sure what you mean. So we just have to accept it.

Lynn what DD is saying is that how full the battery gets shouldn’t be something you have to worry about as you get the same rate for import as you do for export. The only important bit is that there is enough charge in your battery to last through the evening peak as you don’t want to be importing then at the higher rate.

After that, there is no financial benefit to charging the battery up higher, you might as well let the excess solar export to the grid and then import later on at the same rate. If you charge the battery up higher and then discharge it you won’t get back what you put in to the battery due to the AC to DC and back again conversion losses whereas in effect IOF gives you the grid as an infinite lossless “battery”.

Having said that, the rates on IOF are not the best and if you are not exporting that much in the winter due to less solar then it may not be the best tariff to be on.

Tim & Kat’s Green Walk on youtube did some rule of thumb videos on what were the best tariff to choose based on your generation and consumption ratios

geoffreycoan
An excellent explanation 👍I've watched Tim and Kat's since they started the channel, very useful. He did respond to comments about not comparing the Agile Tariff, evidently it is too variable to model. Using Octopus compare with my data,it suggests that I am several hundred pounds better off on Agile.

Moving to IOF this time of year is probably a bad idea unless you really like price certainty and/or simplicity and/or have enough solar panels to still be net exporting each month.

I'll probably move to agile in early November. Slightly worried about various parts of that, including the ease of getting back onto IOF in Spring, how easy it is to get predbat setup and how much the electricity will cost - basically will need to avoid 4-7pm ish usage and perhaps 7am ish too.

TX200 If predbat is an issue have a look at WonderWatt.

Watcher
That's what I am using. It's regularly evolving with plans to introduce a " predbat " style automation for Agile users.

Tenkaykev
Me too!

Take a look at this. I have gone from Flux(import and export) to Eco 7 import (7 hrs off peak charge).
Battery keeps me going during the day and any solar tops the battery up/powers the house. Any really sunny day I might get a tiny bit of export, but last 3 years experience of Oct-Mar is not much.
This checker shows I would be slightly better for export on Intelligent Flux ( but I wanted to stay in control) or Flux (not allowed with Eco 7), but the savings on Import with Eco 7 more than offset the missed export income in my case

https://www.octopriceuk.app/compare

I guess I have to decide if £6 per month is worth avoiding the effort of setting up predbat.

Plus would it be cheaper to stay on IOF or move to agile with a £6pcm fee. One of those difficult to answer questions, so many variables!

TX200 …. Or £4.50 discounted for a year, sure they will work towards making it value for money on other tariffs? Worth it to me, YMMV!😉

TX200 There’s also the cost of the equipment (an old PC, raspberry Pi, etc) to run Home Assistant and Predbat on.

And another option is the beta tariff automations in the GivEnergy portal.

To get the absolutely best result out of Agile you need some form of tariff automations, but if you are prepared to not absolutely need the best financial result then its pretty straightforward, you just charge the battery overnight when its cheaper rate and make sure you have enough to avoid the 4-7pm peak. Weekends are generally cheaper as is when its windy or sunny. Sometimes that cheaper rate is (like last night) around 10p/kWh, sometimes it’s 15p, and like earlier in the week it’s up to 20p. But anyway I don’t think I have ever seen it more expensive overnight than the standard variable rate tariff.

Last week’s prices:

If you don’t have a lot of battery storage then Agile becomes harder to manage without automation.

SteveCook You could always sign up for Agile fixed export - 15p - it's compatible with Eco7 and you might pick up a bit extra income on the few sunny days this winter.

Karen Thanks. I am on 15p fixed export but TBH it is rare that gets the battery recharged and have any excess even on a sunny day during Oct-Mar with 27 panels in the Pennines

geoffreycoan There’s also the cost of the equipment (an old PC, raspberry Pi, etc) to run Home Assistant and Predbat on.

And power!

I have a Pi5 running a HA which draws about 5W, call it 4kWh a month. An old PC would be much more than that.

PianSom True, as we’ve talked about before, the Tiny PC I use to run my Home Assistant uses about 1-1.1kWh a day.

Home Assistant and Predbat is worth it if you are wanting to get in to the whole home automation thing and draw graphs of power usage, etc. If you simply want to charge the battery at cheaper rates then there’s other ways to do it.

I got the Pi for nowt when my teenage son moved out

Watcher I think I'd be mad not to move back onto IOF in the spring, given the high export rate (unless it changes), long off peak, virtual battery (grid) and my high generation to consumption ratio.

geoffreycoan already got a Pi running HA, BCDave's octopus integration, GivTCP and various other things. 😁

geoffreycoan Thank you for this explanation. Many posters seem to use apps to control their usage. But we really don't want to go down that road as we want to keep it as simple but as economic as possible.
Will look at Tim & Kat's Green Walk to see what their comparisons show.
Thanks again.

I’m sticking with IOG for now. We just got a heat pump which has only been on for just over a week properly but so far has run off the 7p juice or the battery so I want to monitor it to see how bad it gets!

SimonClarke Snap - had my HP for two weeks - running on solar + batteries without problems so far. However the installer who commisioned the HP just checked that the rads were getting warm and that the HW was on (tepid). I'm just starting to measure water temps - need more k Type leads though. What should 'commissioning' include? Mine is a Gen7 Samsung.

Slartibartfast been heating dhw for about 3 weeks with no issues. Heating been on this week - we got back from Malta on Monday, was 28+c! Not sure what commissioning requires. Mine is a Viessmann 8kw. Radiators never seem particularly warm but the house is. I had to lower the target temperature.

@SimonClarke @Slartibartfast if your installers are anything like mine, they will do the least they can with setting up and optimising the heat pump. In fact they will probably have set it up so that it produces more heat than it needs to so that they don’t get called back.

We’ve had a heat pump for 2 and a half years now and I’ve learnt a lot about how to run them as efficiently as possible. Key things I would look for:

1. Check how the heat pump heats up your hot water. Mine was set to a hybrid mode of heat pump and immersion heater. Using the heat pump is typically 350-450% efficient, the immersion only 100% efficient. Change it to heat pump only, it’ll take a bit longer but will be much less to run
2. Check and reduce the hot water temperature. Heat pumps are more efficient the lower the temperature, so the lower the temperature, the cheaper it’ll be to run. We heat ours to 48 degrees and people will automatically say “legionella”. Have a look at the article on the heat geek website about Legionella and make your own decision about what temperature you are comfortable with based on your household, how often you turn over the water in the tank, etc.
3. Likewise reduce the hours that the hot water is being heated for. We heat ours once a day overnight on the cheaper electricity.
4. Definitely look at the flow temperatures of your heat pump. It should be as low as possible, basically just replenishing lost heat in the house. The radiators should be just warm but not hot if it’s doing that. You should have a weather compensation mode on the heat pump that varies the flow temperatures with the outside air temperature - this one setting alone will make a big difference to your electricity consumption.
5. Run the heat pump 24x7 (again look at heat geek articles). By all means set the temperature back overnight, but most efficient is to run on a low slow temperature not to heat the house boom or bust when you want it hot.

geoffreycoan ours is pretty much set to your description. I originally lowered the dhw to 48c but have just put it back to 50c and a longer heating time as it was a bit marginal when swmbo wants a proper bath after I have had a shower. Not worrying about legionella as we use a fair bit. I also think I might put it on the same temperature all the time as this is how we ran the oil heating so we are used to it.

If you are worried about Legionella, can you run a pasteurization cycle every few weeks.
I think 65degC for 10 mins should do it?

SteveCook that’s what I turned off!

Legionalla is in most water. Drinking it is OK no problem in the stomach. It gets harmful when in vapour form and gets into the lungs (cooling towers and showers do this). It multiplies when stored in a nice warm environment (like a low temperature hot water cylinder). Heating up to 65degC for a few minutes kills it. But when fresh cold water flows into the cylinder it starts multiplying again.

SteveCook we pretty much empty the hot water most days. As mentioned above the heat geek video on this is helpful. Shower heads that don’t get used regularly are probably the most worrying for legionella - or spanish hotels..

Here’s the article I mentioned https://www.heatgeek.com/hot-water-temperature-scalding-and-legionella/

The traditional heating engineer approach has been to always keep the hot water tank at 60 degrees, but as the article covers, this is overkill and lower temperatures can be used

The control of legionella is not an on/off switch at 60C, most is killed at 50 C if maintained for long enough time.

There is a useful article covering temperature, water turnover and scalding along with risk factors for vulnerable/non-vulnerable people.

https://www.heatgeek.com/hot-water-temperature-scalding-and-legionella/

Looks like an overlap of replies.

I have a Tesla "smart" immersion and every 14 days it'll do a run up to 60'C for 30mins (unless it's already been that hot in last 14 days in which case it resets the timer)

SimonClarke You can investigate my Viessmann 10kW HP here (Public site), run entirely on weather compensation.
https://emoncms.org/app/view?name=viessmann_combined&readkey=d9fa0b89bb710d76148a53d979624a2f
Edge of Sheffield/Pennines, 800' up. Heating has been coming on since start of September. It's not nearly as warm up here as the balmy south but my system has produced SCOP ₅ (run since September 2023).

A lot of good advice from geoffreycoan
I follow Heat Geek advice for legionella.

My flow rates are typically about 30-32C in winter. Design temperature is 40C but this is for coldest day (-3C for me) but highest I have seen in 34C.
So much depends of the installation and the rads matching heat loss on a room-by-room basis. The lower the temp, the more efficient. Mine is set at 20C day and 17C night in setback mode. I had an excellent Heat Geek installer who set everything up to run as cost-effectively as possible for my set temperatures.
DHW is heated once daily usually afternoon (for highest air temp) or night (at lowest rates). I flip between the two.
The HP has been brilliant. House is so comfortable but takes a bit to get used to rads that are barely warm to touch.

It is worth learning about best settings and your heating curve, which is good for tweaking.

Some installers design systems running at higher temps such as 50C or even 60C. These may be designed to run with existing rads and 'cheaper installations'. This can save on new rads but will run much less efficiently than lower design temps so will cost more.

Rob

The problem I've got is that the Hysteresis is too high i.e set HW to 54 degrees - it will heat to 55 but then drop to a low of 42 before it re-heats. I've got to look at the HW control parameters to see if I can limit the drop. However it would then re-heat more frequently.
As for the heating - I'm at the observation stage - no changes until I understand what's going on. First thing - balance the radiators. First rad 5 degree drop flow to return. However the two main pipes that connect to the old radiator system - only one degree between them. Strange.
At the moment there is a Nest thermostat. Glows orange when the heating is on. So its a stat plus 'Water Law' i.e. weather compensation. Is anyone using 'Homely' ...

Rbor I’m not expecting that good a scop as we have microbore (10mm) to the rads in the wall but so far it’s showing over 4 in Norfolk just above sea level! Set 19c morning and evening and 18 the rest. Most of the house is actually about 21/22. As I said I’ll probably set it to be 19/20 all the time because that’s what we are used to. Max flow temperature is set at 50 but not seen it over low 30s yet. Dhw is set to 50c once a day on the iog 7p slot. Basically so far so good. Gained a cupboard and about 10sqm of garden and mains pressure hot water. Lost a few grand…..

Sounds like you guys have got some good heat pump installations. Mine by comparison was a design temperature of 55 degrees and a SCOP of 2.65 - ouch. I wish I knew then what I knew now and had queried and challenged it more.

And yes, that was with almost every single radiator in the house being replaced as well !

In practice this flow temperature isn’t needed except for really cold days. The house has been comfortably warm through the winder once I started understanding the controls and set weather compensation with a flow temperature range currently of between 30 degrees (at 14 OAT) to 52 degrees (-2 OAT).

I wish I knew what my actual SCOP is but there’s no measurement I can find on my LG Therma V control panel and having the open heat pump monitor stuff fitted would cost £500 for the kit plus the installation cost so its just not worth it.

Having the biggest radiators fitted you can is the other bit of key advice I’d give as @Rbor says to reduce run costs. In the 2 years post heat pump install we have swapped the lounge radiator for a bigger one (we originally didn’t accept the installers recommended radiator size and elected for a smaller one, which proved to be a mistake), and put new radiators in the kitchen and utility room, replacing the original (unchanged) towel radiators.

geoffreycoan I persuaded our installer to fit a larger rad in the lounge. All the rest went from type 11 or 21 to 22’s with exception of one which was newer

Rbor https://emoncms.org/app/view?name=viessmann_combined&readkey=d9fa0b89bb710d76148a53d979624a2f

That looks absolutely amazing ! Congrats. Certainly sipping the electricity. Bet you are chuffed.

What size/ type of construction property do you have? Is it highly insulated? I’m guessing it’s quite large as it’s a 10k HP.

I’m not quite sure it’d work as well on my old solid wall Victorian property. But you never know. I did do an initial online Heatgeek quote but it was coming out at £15,000ish AFTER the (English) govt. grant. Eek !

Pete UK HeatGeeks - some of their installers are taking the P. They quoted me 12K after the grant - that included changing all of the rads - for 6K. So I found someone else for £2.5K and changed the rads myself (£700 material cost). Try and get at least three quotes.

This was only a quick online quote. Not a detailed one. Maybe I need to actually get them round for a proper survey… seems like they are getting better and better and with the 7p off peak rate and lots of battery storage. It’s looking more and more feasible for my situation. Maybe not for £15k but if it was half that or less then sign me up !

We had about 6 quotes ranging from 4 - 15k AFTER the grant! Went for a mid one as they were doing more work. Watch out for extras - like a base for the heat pump, electrical work and making good! Some comedy involved…

26Left Tomato Lifestyle EV

Some more info on Tomato now that I've managed to get through to someone more knowledgable on the phone.

The data I'm seeing on their MyWatts dashboard is indeed dummy data - apparently there is sometimes an issue when switching off Octopus onto Tomato because they use the same smart meter data provider (TMA website - incl. explanation of their role) that sits between the meter itself and the supplier in the chain.

Should be resolved in the next few days as the ticket has been raised.

Some other nuggets

• Tomato expect to launch an export tariff "early 2025"
• My smart meter in home device (IHD) won't work currently as Tomato licensing(?) is still underway - hence the use of MyWatts as the data dashboard for the time being
• while n3rgy is no longer accepting consumer signups to view free smart meter data, you can sign up to third party apps to access their meter data instead, e.g. :
• Hugo - supports manual tariff entry (peak and off-peak rates and times)
• Loop - doesn't support ToU tariffs, or even a manual entry
• Bright - not tried as of yet

26Left Was there any mention of how tariff information is made available? The Tomato Agile looked potentially interesting but when I looked there was no real-time data in the website from which I could compare to Octopus Agile. No details of how it was priced, nor whether the daily prices were via API, website, email or anything.

geoffreycoan I don't know - I've not gone for Tomato's Agile offering, I've gone for

26Left Tomato Lifestyle EV (rate comparison here)

which is cheaper than Octopus Go and (IOG for that matter).

26Left Understand. I just wondered if there was anything that came up in conversation about the dashboard and information in general.

At the moment Tomato definitely isn’t for me, maybe when an export tariff comes along I will look again, but the free Greggs coffee, DFS sessions, Free Electricity and Power Up events are all reasons that tip towards remaining with Octopus. Looking at my 2024 year to date import consumption, nearly 13% of ALL my import has been on the free electricity/power up events.

I was joking about the Greggs coffee. Maybe sausage rolls though ….

geoffreycoan Ha. I'm still on Octopus for export so I'm hoping I'll still be able to avail of some of those!

Just finishing up a longish post on this thread re DFS as I'm curious as to whether this is going to be as lucrative this winter, and whether my current situation / setup as hobbled my ability to benefit!

If I talk to someone knowledgeable at Tomato again, I'll ask about Agile.

26Left Thanks, I just read with interest your post on DFS and the linked Axle Blog & Drax articles.

Notwithstanding the Greggs coffees, I believe Scottish Power SEG @ 12p (https://www.scottishpower.co.uk/smart-export-guarantee ) is a better export rate for you than Octopus SEG @ 4.1p (https://octopus.energy/blog/outgoing-faqs/#tariffcombinations)

geoffreycoan I believe Scottish Power SEG @ 12p

They seem to have some odd constraint about batteries - you have to supply a storage schematic diagram:

If you also have a battery storage system, we’ll need an image of the install schematic (or single line diagram) to show that the output from the batteries will not be measured by the export meter. This is due to it being classed as ‘brown energy’, which isn’t eligible for payments in our SEG scheme. The diagram must show where the smart/export meter sits in relation to the renewable installation, battery and grid.

My son's just had an Octopus HP installed (Daikin outdoor unit). Net quoted price was around £2,700 (after BUS grant). Not the best experience with a load of survey cock ups like, them not realising the proposed new HW tank would not fit through the loft hatch. 2nd HW tank arrived which fitted through the hatch but was too tall too tall for the available height in the loft! 3rd tank arrived (horizontal tank) which required the loft hatch to be enlarged & a heavy duty platform to sit it on in the loft (all Octopus omissions so at their cost). As a result my son was without HW (with a 1 year old in the house) for 7 days.
There were some other aesthetic install issues as well which all in resulted in Octopus making "good will" gesture refunds totalling £2,200 leaving just £500 to pay from the original £2,700 quoted price. It's a good job the house is a "fixer upper" which my son & partner plan to do loads of work to because the Octopus install team made a right mess.
A loss leader job for Octopus which they must have put through their books as "training" cos they sure as hell didn't make any profit on this one.
Makes me wonder whether a HP is worth all the hassle for our house? Our gas boiler is only 5 years old & we have 10mm copper microbore in the walls / underfloor to all our rads so do I really want the upheaval & hassle for the time I have left?
The biggest issue for me is the location of the outdoor unit. Where I'd like to put one so I or my neighbours can't see it, is closer than 1m from a boundary fence so that's not allowed by MCS / planning regs. There are no other places in the front or back gardens that I'd want to see one installed so for that reason alone I probably won't be going down the HP route. I might convert to mains pressure HW (from gravity) & have a new HW tank put in the loft to free up some space in the airing cupboard but that's about it.

DD They seem to have some odd constraint about batteries - you have to supply a storage schematic diagram:

If you also have a battery storage system, we’ll need an image of the install schematic (or single line diagram) to show that the output from the batteries will not be measured by the export meter. This is due to it being classed as ‘brown energy’, which isn’t eligible for payments in our SEG scheme. The diagram must show where the smart/export meter sits in relation to the renewable installation, battery and grid.

I saw the mention of needing a schematic and had heard that they didn’t like brown energy exports (there’s a switch in Predbat to turn off brown exports), but the above will be impossible for most battery owners as the export meter is normally on the house grid supply. If you’ve got a hybrid inverter you’ll be out of luck as well.
I’ve got meters on both my FIT array and the GivEnergy inverter connection to the main supply but I’m sure they won’t accept them as ‘certified’.

OK, so not Scottish Power then. Hmm.

CGoode I had similar but not quite as bad issues with getting the buffer tank for my ASHP into the loft. Had to take the trim off the loft hatch and then it only just fitted in. Fortunately it went on the platform where the cold water tank had been so no loft reinforcement required.

If you have a modern enough gas boiler there’s not a lot of incentive to get a heat pump other than the grant which probably won’t last forever. Does make you more energy independent if you’ve got solar and batteries - our net consumption bill for the 12 months to mid August (when we got our export tariff) was -£14; as I say, I can generate my own electricity but not gas.

You can get a heat pump installed if it’s less than 1m from the boundary fence, it just doesn’t count as permitted development and will need planning permission. Oli ‘speak to the geek’ had a series of videos on his own heat pump journey as he lives in Wales and the Welsh boundary fence limit is 3m. Started needing noise surveys and all sorts of other stuff so not straightforward in his case. Probably best to ask your local council what their requirements are

geoffreycoan better export rate for you than Octopus

(whispers quietly) Octopus don't appear to be very good at downgrading your export tariff when you move import tariffs - currently they still have me on Fixed at 15p/kW...

26Left They catch up with you though - ask @geoffreycoan 😃

We are waiting for an Octopus install. Initial quote was £2050 but we didn't go ahead inside the 30 days. The price went up to £2450.

Then, after we had gone ahead for £2450 they sent an offer of £2050 which included a £250 discount. They have agreed £2050 less £250. Winner.

Any feedback on Daikin?

Vestas certainly true, in October 2023 I moved from Octopus Flux import and export to Agile import, but Octopus left me on Flux export 🎉😁

5 months later in February 2024 when a new version of Agile came out they finally realised the mistake, that I should have been on 15p fixed export, and back-billed me all the way back to when I left Flux.

I did complain that this was unfair as it was their mistake, that my export behaviour would have been different on 15p fixed export (no peak exports for example), but didn’t get anywhere. In the end it was only about £20 difference on my bill so wasn’t worth arguing any more about

I have put together some general points to consider when going for a heat pump installation together with links that I have found useful. These should supplement earlier comments and the list from geoffreycoan.
These are my opinions built up from my preparation for my HP installation a year ago and snippets I have picked up since. There may well be better advice so don't treat as the gospel truth. Sorry for the doubtless typos.

1. Do some research and learn about what to expect. Youtube videos are good. It is worth looking at Heat Geek videos: https://www.youtube.com/c/HeatGeek.

2. Price is a big factor of course but you do get what you pay for, as is the expertise of your installer.
   Big companies such as Octopus, are going for the straightforward installations, typically newish premises (say 1980 onwards) and not too big. They have teams to carry out heat loss survey and different teams for the installation. Smaller setups will often have the same person for heat loss survey and installation. They will also look at related important issues .....

3. How many radiators will need changing? My house in a 1920s detached, one of the first to have cavity insulation (about 2 am gap!) Get more insulation in that loft!

I did have mainly K2 rads (2 fins), about 10 cm deep and some old K1 rads (1 fin) about 5 cm in depth.
Half of my rads were changed to K3 (3 fins) ₁₅ cm deep I don't have any K1s any more. The wall footprint of K2s and K3s is the same as single fins (K1) but they come out further from the wall. K3s give out more heat. The more heat from a rad, the lower the temp it will run.
The lower the temp, the more efficient.

Rads are not that expensive and some folk save costs by changing their own.
So companies promise to keep existing rads, run at 70C and these are not going to be efficient – they will be cheaper to install but more expensive to run.

There's a great series of articles here: https://energy-stats.uk/blog-summary/.

4. Which heat pump?
   To get a government grant (£7500), the heat pump power must exceed the heat loss and the installer must be able to get MCS accreditation. My house's heat loss came out at 8.3 kW so I finished up with a 10 kW heat pump.
   Heat pumps > 7 kW tend to have 2 fans and are larger, essentially two 1 fan models, one of top of the other.
   The volume of the HP means that you need planning permission!! (Cost me £230 and some angst). There is pressure for this daft rule to be relaxed along with the 1 m gap from neighbours (3 m in Wales, I believe). But most HPs seem to be 5 kW or 7 kW, single fanned models and there is no planning requirement for size.

See https://heatpumpmonitor.org for a good comparison of HP brands, installers and COPs.
The best performing seems to be Viessmann, Nibe (more expensive) with Vaillant not far behind (there are loads of Vaillants). You can compare prices here https://midsummerwholesale.co.uk and get further info from brand websites.

5. Where is the water cylinder going?
   You need one .... and it needs to be sorted. See the sorry tale from CGoode earlier for potential issues with getting a cylinder into the lost.
   Mine was fitted into an unused under-stairs cupboard. Airing cupboards (if you still have one) may not be big enough. Garage?
   You can generate hot water by phase change transfer of heat. See Sunamp in https://midsummerwholesale.co.uk (These are more expensive). No cylinder is then needed and systems are much less bulky. Most systems though use a water cylinder.

6. Heating the water in the cylinder.
   It will usually be cheaper to heat from the HP but this does drag down the COP (less efficient than space heating).
   I have a 200 l cylinder, brand new and super-insulated. It loses about 1 kW a day.
   I heat to 43C but use the water straight off with no dilution of heat with cold water. If you need a lot of hot water, use higher temperatures and cool the water down. Obviously costs more.
   Heating using excess solar sounds good but you don't get the magnified 'COP heat' from the input.
   An immersion heater, which will always be within the cylinder if needed, will also be 1:1 electricity to heat.
   Use afternoon when air temp is higher or use low rates at night but with lower air temp.

7. Noise, what noise ....... Typically about 55 dB when working and negligible on tickover.

8. Cost.
   I have an excellent COP and my HP is cheaper that my old combi gas boiler. Electricity prices need to come down compared to gas (currently ~ 4:1) so you need a COP of 4 for parity. Hopefully this will change, either be electricity prices coming down or gas up! I think you should be looking at a COP of 4. SCOP is the instantaneous COP over a year

9. Air to air HPs.
   These systems transfer heat to units on the wall. These are solely for space heating and you need a different way of heating water, which can be Solar diverter (e.g. Eddi, iBoost) or immersion. Installation can be quicker and involve less disruption.
   Many great videos here: https://www.youtube.com/@TimAndKatsGreenWalk

10 Microbore piping and buffer tanks.
Ideally, microbore pipes (10 mm) need replacing with standard 15 mm piping to rads. There are examples of systems using microbore. I would not want one myself! But replacing micropore is a disruptive with more expense, much of it from labour costs. An installer will take a primary feed using 28 mm piping from the HP before splitting off to rads with 15 mm piping. This idea is that the temperature across a radiator drops by less than 5C (∆T).

Typical residential installations won't need a buffer tank but it depends on the size of the installation.

11. Air source or ground source.
    Unless you want your garden or a field dug up and are willing to spend lots, use air source (must be 99% + of residential installations)

12. A good installer is worth their price in gold.
    Watch out for the cowboys. I read of one poorly performing 16 kW installation where another installer checked the heat loss. It came out as 8 kW!

That's enough for the moment.
If you are interested in getting a HP, do some research. There are plenty of other good videos.

Hope the comments are useful. I nice way to while away a dreadful rainy afternoon. On the plus side, I am getting some nights with lower Agile import rates ......

Rob

Heat loss calcs are important - I had four of them all different. Try using HeatPunk - it's free. Another alternative is to buy yourself a copy of the Domestic Heating Design Guide - £30 - and use a pencil. Or sign up for Heat Engineer software - £10 for a single design. You'll need a laser measure and have to know every detail of your house fabric. This is where the professional Heat Loss Surveyors go wrong - they guess. My complication was a MVHR system, I'm not sure that the Octopus accessor new what it was.
Final outcome - the installer ignored the report and fitted a 8kW unit. His attitude is 'I've been installing HPs since 2007 - I know better'. Did he check the radiators I had upgraded - no. Did he check the pipework - no. By the way HLCalc was 4.3 to 4.8kW.
Interesting e-mail from them:
_Please note that any modifications or adjustments made to the system’s settings after commissioning, without the approval or involvement of a certified installer, may:

_Invalidate the warranties provided by the installer or manufacturer.
Result in suboptimal performance, inefficiencies, or potential system failures.
Lead to non-compliance with industry standards, regulatory requirements, and safety protocols.
Affect the system’s eligibility for government incentives, rebates, or subsidies._

_To ensure continued compliance with the Microgeneration Certification Scheme (MCS) standards and maintain the integrity of the installation, we strongly advise that all maintenance, adjustments, and modifications be carried out by an MCS-certified professional.__

Idiots.

Rbor The volume of the HP means that you need planning permission!! (Cost me £230 and some angst). There is pressure for this daft rule to be relaxed along with the 1 m gap from neighbours (3 m in Wales, I believe). But most HPs seem to be 5 kW or 7 kW, single fanned models and there is no planning requirement for size.

In my case the neighbour's house is 10-12 metres and the projected noise level with the HP side on was assessed as 41dB, ie too high. We spoke with the neighbour and determined that their 'bedroom' which was too close for the noise level was actually a bathroom. The surveyor is coming to reassess the siting. The initial plan was backing to our 1st floor ensuite. Will ask about the HP noise level for US!

Our energy requirement is assessed as 7677kWh for heat and 2125kWh for water. SCOP for heating is 3.48 and 2.754 for water. The HP will be a Daikin.

Roy124 Our energy requirement is assessed as 7677kWh for heat and 2125kWh for water. SCOP for heating is 3.48 and 2.754 for water. The HP will be a Daikin.

Similar heat loss to me, which will presumably result in the 9kW unit, which seems to be considered a bit of a handful. (That's the one I have.) Problem is that it's part of a family going up to 16kW, and as such, doesn't modulate down as far as you might hope in the milder weather. (Whereas the 8kW unit is the top of its 4-6-8 family, and modulates down much further.)

DD doesn't modulate down as far as you might hope in the milder weather.

What does that mean?

Roy124

Oh, hang on - sorry, I misread your post. You gave the annual heating requirement, whereas I mistakenly read that as the heat loss when it's very cold (ie ignored the units). My annual heat requirement is rather more than yours, so I assume so too is my heat loss.

Modulation is just getting the heat pump to reduce its heat output to match the required heat loss, which varies with outside temperature. It needs to be able to output the full calculated heat loss when it's, say, -2 degrees outside, but needs much less at this time of year, when it's only a little below desired room temperature.

Gas boilers just tend to run at high power for short periods at a time, whereas a heat pump wants to run at low output the whole time.

Roy124 41 dB is not loud at all.
Was the 41dB estimated at 10-12m away? This seems very excessive for a modern HP.

Try monitoring the dB from the flue of gas boiler.

I did a search on Google for 'How loud is 41 dB?' and it equated to 'a quiet library'.

Rob

Slartibartfast I used Heatpunk and my estimation was very close to what my installer obtained in the detailed heat loss survey. This considers areas, U values, windows, number and type of rads, etc.

His attitude is 'I've been installing HPs since 2007 - I know better'.

This sums up everything that can be wrong! It sounds akin to licking a finger and holding it up to the wind.

A HL of 4.3-4.8 ponts to a 5kW HP. I know that Vaillants typically punch a bit over their weight also.
8kW is too big IMHO

For a really detailed discussion on choosing size of a heat pump, see:
https://energy-stats.uk/what-size-heat-pump/

Rob

Rbor A HL of 4.3-4.8 ponts to a 5kW HP. I know that Vaillants typically punch a bit over their weight also.
8kW is too big IMHO

One thing to bear in mind is that the 8kW Daikin outputs 8kW at about +7 degrees. At -2 degrees it will be down quite a bit - can't remember exactly, but closer to 7kW. Whereas the vaillants specify their heat output at much lower temperatures.

And as I said above, the daikin 4kW, 6kW and 8kW are (from what I've heard) the same hardware, with only difference between them is that the max output is software-constrained. So the behaviour at lower output will be much the same. So makes little difference in practise which you actually get. (But the step up to 9kW is more significant than it sounds.)

(I wonder if we should be a separate thread for heat pumps, rather than taking over "winter strategy" thread.)

Rbor 41 dB is not loud at all.
Was the 41dB estimated at 10-12m away? This seems very excessive for a modern HP.

Indeed, the potential noise at the bedroom next door when the maximum acceptable is 40dB - I was told.

Roy124

DD I agree about a heat pump thread.
Do you want to start one with a comment here to continue discussion on heat pumps at XXXXXXXX

As an aside, I have just measured the sound that my fridge makes and it is 39 dB.
Where is the source of this 41 dB 10-12m away estimate?

Rob

Winer strategy - we have 4kWp solar facing due-south, AIO 13kWh/6kW, 10kW G99, on Octopus IOG, and 15p/kWh export.

Cost-wise, it's still working out best for us ( October so far net income of £1/day) to fill the car and AIO overnight @ 7p/kWh (AIO fixed at a modest 3kW and forced-import for the whole 7p time window so the house runs on-grid all night too even after the AIO is full) and run the house from the AIO during the day.

Export all solar if there is any, and dump the remainder of the AIO to the grid in the evening peak in two stages controlled by home assistant. A 3kW export starting 1700 and ending at either 2000 or 30%SoC whichever comes first and then a manually triggered (but auto calculated) export later on which works out the optimal kW export (usually 2-3kW) to get the battery to <10% at midnight.

DD Pending a specific thread, I see my heat requirement is marginally below 8kW with hot water bringing it near 10kW. The Daikin unit is only 8kW. I will speak with the surveyor tomorrow.

Roy124 There’s an interesting article on deliberately under sizing your heat pump on Protons with Breakfast, a blog that’s worth reading https://protonsforbreakfast.wordpress.com/2024/10/08/deliberately-under-sized-heat-pumps/

But in general you would need to size your heat pump for both hot water and heating as otherwise you will be short on capacity in the depths of winter. If you have a source of secondary heating then that might be OK as the article explains.

You may be able to reduce your heat demand by increasing the size of your radiators more, triple panelled, wider ones, etc but unlikely you can shave 2kW off. You don’t really want to be running your heat pump flat out to keep the house warm as that’s when they are least efficient, you want a bit of over-capacity, but not too much,

NorfolkMustard Winer strategy - we have 4kWp solar facing due-south, AIO 13kWh/6kW, 10kW G99, on Octopus IOG, and 15p/kWh export.

Cost-wise, it's still working out best for us

Most people that can have IOG or Go do seem to swap to it for the winter if they’ve been on Flux or IOF for the summer, so seems a good strategy as long as your battery is sufficient for your home needs. As you say, export solar and any excess in the evening, charge up on cheap rate overnight.

geoffreycoan no radiators. We have UFH upstairs and down. The new cylinder will have an immersion heater. We have a fan heater in the living room.

Roy124 Pending a specific thread,

created: https://community.givenergy.cloud/d/5083-heat-pumps