Best tariff or strategy for solar/battery 16 May 2022 at 1:43PM in Green & ethical MoneySaving 15 replies 1.2K views

Nick_Dr1

Having recently had 4kW solar and a 7.2kWh battery installed, I'm wondering what's the best current strategy for getting a good return?

I know this is a "how long is a piece of string " question, but there are probably some general rules that can apply.

I'm thinking that a low night rate is good as it can charge the batteries, which can then support the house in the morning until solar kicks in. Solar can then recharge the batteries to cover evening use.

This will reduce usage to zero on a good solar day, but on a bad solar day, I will end up paying for "normal " electricity in the evening at a higher rate (but I'd have had to buy this electricity at whatever normal rate I was on anyway).

Has anybody done a similar calculation recently with current rates for their useage, to give me a clue, and what provider are they using?

Alnat1

It will depend a lot on your expected solar production, general electric usage, how much your overnight load is, do you heat your home with electric, is your seasonal use similar,  maybe post some figures

arty688

It will also depend on if you have an EV or not , as the best TOU tariffs require an EV.

EcoScruples

I'm in exactly the same position, I'm looking at going Octopus Go so I can take advantage of the cheap rate electric to charge my battery to be able to reuse during the cold winter days.
Obviously I need rhe EV which I'm sorting but it seems worth the calculations to he able to use electric at a quarter of the price when solar just can't do it during Nov, Dec, Jan & Feb

arty688

Also octopus Agile will probably be OK over the summer, wouldn't like to be on it in the winter though

Nick_Dr1

Alnat1 said:

It will depend a lot on your expected solar production, general electric usage, how much your overnight load is, do you heat your home with electric, is your seasonal use similar,  maybe post some figures

No EV at present
Good performance from the solar. Its 4kWp and I am seeing 20-22kWhr daily production on good days (in May - I only have 3 months data.). Bad days about 5kWhr so far.
Average use of about 16kWhr per day, but that includes excess being diverted to the hot water (iboost). Over three months solar has reduced my bill by about 80% so the standing charge is the most significant cost
Heating is oil. Overnight basic load appears to be about 200-300W.
On a good day, I can be totally self sufficient in power consumption. In other words , normal use means that at this time of year on a sunny day, solar and battery can give all the energy I need for 24hrs.
The winter will obviously be different - I won't have enough solar to run the house or charge the batteries much. 
I guess in the winter I can get maybe 1/2 a days electricity from charged battery/solar (if I can charge the battery overnight sensibly)  so would need to buy 6 to 8kWhr per day. In the height of summer I wouldn't need to buy anything except standing charge.
Are there any tariffs that I should be considering? Do I actually need an EV for Octopus go?

EcoScruples

You sound very similar to me (although my install is now happening in June).
I also have an oil fired boiler so in the winter I'll use that to heat the water as I'll be running the heating anyway.
I've been measuring my oil tank every day and an hours use to heat my water per day actually uses very little oil.
You do need an EV charger and now an EV I believe for Octopus Go. I haven't found any other tariffs that would fit the use of a home battery apart from economy 7 which isn't really what I want.

arty688

You don’t need an ev charger just an ev. I charge mine from a 13a socket. You need the right charger or car for intelligent octopus which is another option.

michaels

Edf have a tariff with 5 hiurs at 4.5p but very expensive for gas and I dont think their is an electricity only option

Magnitio

I've recently switched to Agile Outgoing Octopus where the rates change every half hour after realising how much more I could be getting for the excess energy we currently produce (£55.30 last month compared to £14.59 at fixed rate). It's a bit of a gamble if the price is very high when dark winter days arrive, but you can choose the best rates of the day to charge the battery.

random321

I'm just having a 5kW system installed with 4.8kWh battery and am also wondering which tariff to choose. I'm thinking Octopus Go as we do have an EV so especially over winter months will charge the solar batteries and car between 12.30am - 4.30am, and also program dishwasher/washing machine etc to run during the same time.