Hi folks,
I have 4.86kw solar panels and a 9.5kw battery, 3.6kw inverter.
My installer has just offered me a good deal on either an additional 5.2kw or 9.5kw battery.
Would appreciate folks opinions on if it's worth going for in general principle? I can afford either, but wondering if it's worth it financially.
Cheers
Scottishcammy I think it's impossible to say without knowing your individual circumstances. Do you aggressively cycle your battery to buy low/sell high, or just use it as a buffer to maximise self-consumption of solar? What's your typical daily consumption.
Eg my own 9.5kWh battery is probably more than I need at the moment, but when heat pump arrives, I'll probably be wishing I had more.
I had a very similar system to yours installed in April last year. GE 3.6kW Hybrid inverter, 10 x 415w panels on a ESE roof & 9.5kWh Gen 2 battery. Zappi & Eddi also installed at the same time. No HP (yet) so I'm still on gas for heating & HW.
After the install all went well & I managed to self consume up to 90% of all my generation until the winter months arrived when, depending on usage & without much solar top up, the 9.5kWh battery kept running out from 12noon onwards (we are at home most days). Also, I was constantly second guessing the next day's weather in order to maximise solar battery & EV charging during the day to avoid having to pay to unnecessarily overcharge the battery at night or use grid power during the day (I was a std variable rates & I had no export tariff at that time).
I therefore decided to add an extra 9.5kW battery & an extra 5 x 425wp panels on a NW roof to catch mid afternoon & evening generation & these got installed earlier this year. The 2 x 9.5kWh batteries now last throughout the day until the cheap rate tariff kicks in which is great.
After Octopus approved our EV & charger combo I switched to Intelligent Octopus Go earlier this year & got an export tariff so now my charging routine is different.
Irrespective of the next days weather I now charge the batteries to their max every night between 11.30pm & 5.30am @7.5p/kWh which means any excess generation the next day goes straight back to the grid & earns 15p/kWh. This is great for the summer months & I am starting earn some decent export income (on sunny days) to offset the overall energy bills. However, with double the battery storage installed, it now takes longer & costs more to get the batts charged up & keep them at 100% to force any excess back to the grid & get paid for it.
I guess it's a "6 to 1 half dozen the other" scenario. The extra battery capacity helps massively during the winter months but could be construed as a hinderance during the summer. I think this is why some Octopus users switch tariffs from winter to summer. Personally I'm not sure that makes any sense for us but I'm willing to be persuaded otherwise.
Time will tell after a full year of use how much extra I have manage to save by adding another battery & extra panels. However, this year I have already claimed back £1,500 from my Octopus account because I was over £1,800 in credit (I didn't reduce my DD payments after the solar was installed). I have also now reduced by DD monthly Octopus payments by over half so for me the whole solar thing is starting to work.
As ever though, & like many others on this forum, I'm still tweaking how I use & control the system to suit what we need & achieve the best results.
Based on my experience the extra battery was worth it but getting the right size will depend on your daily usage & any future plans you have e.g. adding a HP to replace a gas boiler. Battery prices have dropped quite a bit & there's no VAT now so going larger is not so much of an issue now than it was a 6 months ago.
I hope this helps.
CGoode owever, with double the battery storage installed, it now takes longer & costs more to get the batts charged up & keep them at 100% to force any excess back to the grid & get paid for it.
There's no necessity to fill batteries to 100% in order to force export. You can either just reduce max charging power to 0, or use the timed pause feature on later firmwares to do that on a fixed schedule.
The advantage of leaving some room in the batteries is to avoid solar clipping if generation exceeds max AC output of the (hybrid) inverter.
DD 👍️
Interesting thread as I was just pondering if I should look at a second battery … for winter months where I suspect I will be in the same boat as you, I have 15x 435 panels and 9.5kw battery.
Am willing to bet that come winter I’ll be flat by noon only because like you, am work from home etc.
Am yet to get my export MPAN though
FunkMaster ike you, am work from home etc.
There's also two of us working from home, and a 9.5kWh battery is easily enough to run all day. Eg looking back through logs, on 19th December there must have been virtually no sun since the charge level was decaying all day, and it still made it to 10pm with 6% left.
(I see I must have still been experimenting with solar forecasting back then, since I was varying how much I charged overnight from day to day. When there was sun forecast, I was only charging to 60% or 80%.)
I've enquired the same from EON, as there's no way my house will run from the battery for any prolonged length of time on the battery, just need to look at cost vs ROI
I tend not to look at ROI as for me it’s a sunken cost, it’s more how it impacts me month to month as in 10 years I’ll have forgotten how much I paid for solar.
Im sitting at about 59% right now from a full charge but obviously not running heating or any stuff like that, so imagine in winter, by the same time it will be closer to 49% and will that take me through to the 23:30 cheap rate. Not sure … seems it’s about £4500 to install a second 9.5kw battery (considering the trade price is just short of £3k, feels steep to install a second one.
FunkMaster but obviously not running heating or any stuff like that
Do you have gas, or electric heating ? We're currently still on gas, but the electric pump is horribly inefficient, and IIRC conumes about 200W. Modern pumps, I'm told, use a tiny fraction of that.
What's your typical daytime baseload ?
DD My CH pump uses around 35watts.
FunkMaster I also have a high energy usage person in the house - my wife. The kettle is on every 1/2 hour, the washing machine never stops & in winter the heat pump dryer is on as well. During Dec our daily average consumption was 25kWh so the 9.5kWh battery didn't last long.
We sit around the 17kwh stage per day but can shoot to 20 (depends on what’s happening) … got one of those hot tubs that is on all the time, haven’t worked out exactly how much it uses but am sure it contributes (in half a mind of draining it in the middle of winter).
Feels like a second 9.5kw would give some benefit …
To be honest I am only into 5 days of having solar so don’t have enough data points of how effective this is, but just reading what others are doing and more particularly trying to see what winter will be like …
FunkMaster We sit around the 17kwh stage per day but can shoot to 20 (depends on what’s happening) … got one of those hot tubs that is on all the time,
Yikes! How does that split between overnight and daytime? (I assume you run as much as you can directly from the grid overnight?)
How much heat does a hot tub lose when it's not in use? Is it reasonably insulated, or does it go cold pretty much as soon as you stop supplying it with power?