We have 2 5.2KWhr batteries but currently don't have enough solar to reach 50% charge. We're not on any smart tariff.
What is the collective wisdom about turning one of them off over the winter months? I'm interested to hear your views especially if you can back them up with science/economics. I want to lengthen the batteries life rather than shorten them.
I have the same set up, am on Octopus Flux so charge overnight at about .16p and used that power through the day rather than paying .28 or .39p pKwh. Might be worth you looking at? Octopus offer other tariffs, but this works for me.
The batteries are there to be used, switching them off is not saving/making you any money for your investment.
Just my view.
If I were you I’d get on a smart tariff and use the batteries to lower the average cost of your imported electricity, plus they will stay on and can be topped up with any excess solar.
For me the use of a smart tariff and off peak charging has massively reduced bills and the time for the system to repay the investment.
Why not get on Eco7.
You get 7 hrs of half price charge each night and 10kWhrs of storage will probably get you fully through the day.
If you have to do a bit of day top up, on Eco7 it is not punitive.
That will keep your batteries warm and cycled as well
Not sure if it's the same for all battery chemistries, but I think Li batteries are happiest when kept around 50%. Turning off for long periods could allow charge to run low, which isn't so good for them - if you do turn one off, probabably best to charge it up to, say, 75% first ?
Could consider Octopus Intelligent Flux tariff - they'll take control of your battery for you, and (claim to) operate to minimise your costs. I don't think it has the cheap overnight slot, but may work better for you. Otherwise Flux or Eco7 as have been suggested.
I ended up on Agile after Flux (had a brief stay on variable tariff which I regret whilst battery wasn't giving me even 10% of full charge), topping up each day at lowest rate, one day 20-25kwh cost me 75p and that is just for import as I cant find a way to get daily costs to show except on a 3rd party app and that doesn't include export.
Going by Givenergy Smart Tariff thing for 19th November I imported 22.661kwh and I earned £0.298 and export I earned 61p 😃
But from 16th to 23rd of November
Import 124.570kwh £16.710
Export 17.601kwh £2.40
With a smaller battery id have topped up at cheaper rate and paused discharge outside of the peak rate (4-7pm) but even still and if I had no battery id have made quite the savings load shifting.
In hindsight I would have just gone to agile and load shifted, would have still saved quite a bit without a battery.
This is a REALLY good site for having a peek at the various tariffs.
https://energy-stats.uk/octopus-agile-eastern-england/
I'd be wary of switching one off as it may cause problems when you come to switch it back on. I would leave it alone, or as the others say find a better tariff if you have a working smart meter.
If you think switching off a battery might be worth doing contact Givenergy support and see what they'd advise. There may be steps to take to protect the battery whilst it is switched off (say a minimum charge), or to ensure it can be switched on and smoothly rejoin the system.
Batteries have a job to do without solar, you need to think load shifting. Collect cheap rate electricity at night and deploy it during the day effectively doubling your off peak usage. Batteries are designed to be charged and discharged, if they wear out then replace them with something better and more efficient. Not using batteries in winter is the equivalent of having clear plastic sofa covers to make your sofa last 20 years but you never get to sit directly on them!
The warranty requires it to be connected to the internet I believe, as will firmware updates.
Best case, lots of firmware to do, worst case battery chemistry doesn’t like deep discharge so a battery could have a much shorter life, reduced capacity or be a brick.
If you have two batteries I’d get on a ToU tariff and charge both batteries to 75%. Use what you use and work out what you need to add to keep the batteries above 20% by the end of a day and charge that each night.
Let the solar export if the export payment is higher than the off peak import prices.
Windy Miller unless your living on a barge, I'd be charging overnight on a tariff suggested by other people on here.
I'd leave them on and consider a smart tariff. There's not many days in winter when there is absolutely no solar you might as well have it and it's almost certainly better for the batteries.
I’m on a std fixed rate tariff (tied in until the summer) but thinking of setting an overnight charge to circa 70% (leaving some room for solar charge) through the winter months to keep the system ‘working’ and exercising the battery capacity range.
Will review tariffs next summer and see what will work for me.
Windy Miller A Time of Use (TOU) tariff is the way to go, whether it is one of the Octopus ones or a TOU tariff from one of the others.
If you can't have a smart meter for any reason then an option is metered Economy 7 with non smart meter meter(s), ask your existing supplier about their Economy 7 tariff.
If you are open to a smartmeter then don't mention Economy 7 unless they actively market it, that (from experience) could confuse them, (or perhaps gives them an excuse/solution that they hope you will believe).
To give you an idea on the economics: The standing charge will be about about the same. The kWh cost will be approximately 30% (more probably slightly less) of the ordinary kWh cost.
In our case 94% of the kWh's we consume are charged at the off-peak rate. Only 6% are charged at the standard rate. In our case this has reduced the actual total electricity bill by 55% compared to the standard tariff, a £64 per month saving at present, although of course that will reduce as the solar contribution increases in the new year.
Might be worth doing some sums to see if the savings from a smart tariff are enough to cover exit fee from fixed tariff.
kram had a good look at tariffs lastnight and I don’t have an EV or HP so that rules a lot out.
I’m also on an old FIT with 50% deemed export payment, and don’t have an export MPAN.
Seems I’ll lose the deemed export if I try to get an export MPAN.
Conclusion is that for a few winter months I’m going to save less than I will lose by changing things. So staying as I am for now.
treborUK At the moment, in my area, Octopus E7 is 14.5p overnight, compared to standard rate of 27.5p. If you fixed around 6 months ago, your rate is probably similar to that, possibly a little higher? So if you consume around 10kWh per day, mostly imported, you'd be saving around £1.30 per day on E7 (neglecting battery round-trip losses). If your exit fee is around £60, it would be covered in about two months. But if it's more than that (and I think recently they've been over £100 per fuel), then once we get into spring you'll be starting to generate more, and the daily benefit will get smaller.
(Don't forget that the exit fee is waived 49 days from the end of the tariff, so you don't need to wait until the actual end date before switching.)
Thanks everyone for your views.
I'm currently with Shell energy and expecting to be moved to Octopus very soon where a smart tariff becomes an attractive proposition.
I did some calcs on our typical usage. We use 16 units each week day and 22 units on 2 laundry days. Currently averaging 3 units off the panels each day and could potentially time shift 10 units using the batteries. This pattern currently costs £28 with Shell, would cost £21 with Octopus Flux and £16.50 with Octopus Go although I don't have an EV.
Maybe saving £70 each winter is better than prolonging the life of the batteries.
Windy Miller Are you at home during the day?
If so then Octopus Agile is probably the one to go for. We're pretty much the same consumption/generation as you.
This month is the worst we've had so far (for various reasons, including a peak-time calibration charge) in terms of average import unit cost over the month but it'll probably still be under 16p/kWh (inc VAT). Month before it was 14p, month before 13p etc etc.