How to get more from your solar battery
Most of what a solar battery saves is decided by what it is told to do, not by the battery itself. These are the eight things that moved the saving most in what we measured: a full year of 20 modelled homes, and one real home’s autumn. Each links to the guide with the full figures.
Planned to the prices, the same battery saved two and a half times as much.
The same 9.5 kWh battery and 4 kWp of panels in each of 20 homes, for a year on Agile with Outgoing Octopus’s fixed export rate. Saved a year against the same home with no battery: £170.99 left to itself, £246.20 on a routine reset by hand every day, £431.13 planned every half hour.
- 1. Plan it every half hour, not on self useSelf use only stores spare sun. Planned, the battery also fills from the grid when power is cheap and holds its charge for the half hours that pay most. That was the £431.13 against £170.99, and it beat the hand-set routine on all 20 homes. The ways to schedule a battery, compared
- 2. Get paid for what you exportWith no battery at all, moving the same homes on Agile from nothing paid for export to Outgoing Octopus’s fixed 12p was worth £408 a year. If your spare sun earns nothing, start here. It costs nothing. Is a solar battery worth it?
- 3. Pick a tariff your battery can useOver the battery left to itself, planning saved £85.81 a year on Agile with nothing paid for export, £193.83 on Go and £278.86 on Flux, which pays most for export in the early evening. Agile with the fixed 12p export rate left the lowest cost for the year, £7.68. Octopus Go, Agile or Flux?
- 4. Choose the export tariff by when you exportFor a real 27 kWh battery and 13 kWp of panels in the North West of England, over 34 days this autumn, the flat 12p of Outgoing Octopus came out £12.15 ahead of Agile Outgoing. A big roof sends out most at midday, when Agile Outgoing pays least. Which export tariff pays more?
- 5. Know your export limitMost homes may send 3.68 kW to the grid. For the same real home on the fixed 12p rate, its own limit of 6.65 kW was worth £13.24 over five weeks against being held to 3.68 kW. The figure is in your paperwork or your inverter. What is an export limit?
- 6. Don’t store everythingStore a kWh of sun when what you would pay for it later beats what you are paid now, which is most of the time. When the battery will be full anyway, or the evening pays more than the night costs, selling wins: selling in the evening and refilling overnight cleared 7.2p a kWh on 21 of 35 days this autumn. Store solar or export it?
- 7. Keep it working in winterIn winter the panels make about a third of what the house uses. Left to itself, the battery saved £25.04 from November to February. Planned, filling from the grid in the cheapest hours, it saved £112.42. Do solar batteries work in winter?
- 8. On Agile, follow the prices every dayAgile’s cheap half hours move from day to day. Over 32 days this autumn the same real home paid 12.99p for each kWh it bought, against a price cap of 26.11p, while Agile’s own average was 28.40p. From 10am to 4pm Agile averaged 17.82p, less than the 25.00p from midnight to 6am, so a battery set to fill every night paid more. Is Agile worth it with a battery?
The year: the average of 20 modelled homes, 1 October 2025 to 30 September 2026, against the same home and tariff with no battery. The autumn: one real home, 3 September to 7 October 2026 (for Agile, the 32 days from 5 September). Standing charges are left out.
A bigger battery saves more, but each extra kWh saves less.
The same 20 homes with 5, 9.5, 13.5 and 20 kWh, planned on Agile with Outgoing Octopus for a year. Doubling the battery from 9.5 to 20 kWh added £62 a year, far less than planning it did.
What size, and what it is worth
- Each extra kWh saved less£14.76 a year for each kWh from 5 to 9.5 kWh, £7.34 from 9.5 to 13.5, and £4.96 from 13.5 to 20. What size solar battery do I need?
- Your use decides itFrom 9.5 to 20 kWh added £43 a year to the homes using under 4,000 kWh, and £97 to those using over 6,000.
- See the figure for your own homeYour tariff, your battery and your yearly use in: what planning saved the modelled homes nearest yours. Solar battery savings calculator
Before you change anything.
These figures are strong evidence, not a quote. Here is what moves them for your own home.
All our guidesWhat is the biggest single thing I can change?
How the battery is scheduled. Planned every half hour, the same battery in the same homes saved £431.13 a year against £170.99 left to itself. That was a bigger difference than doubling the battery from 9.5 to 20 kWh, which added £62.
Do I need to change my tariff?
Not always, but check that it pays you for export: that was worth £408 a year to these homes before any battery. Which tariff is best then depends on your battery and roof. With a 13.5 kWh battery and 6 kWp of panels, Flux paid the average home £400.49 over the year.
Will these figures match my home?
Your use moves them most, then your panels, your export limit and your region’s prices. The 20 homes are modelled: real households’ smart meter readings with a modelled roof and battery. The 27 kWh home is real, over one autumn.
What does Orza cost?
Nothing during the beta, and no card is needed to join. It plans your battery every half hour for your own tariff, roof and home, and shows each decision and what it saved.
Get more from the battery you have.
Free during the beta. Connect in a few minutes, and start in Monitor only.