A solar battery in summer: leave it to the sun, or plan it?
It depends on how export is paid. Where it earns nothing, planning added only £3.91 from May to August on Agile, across 20 modelled homes with a 9.5 kWh battery. Where it is paid by the hour, planning roughly doubled the summer saving: on Flux, from £76.01 to £179.35.
What these figures rest on: 20 London households’ real smart meter readings (Low Carbon London) with a modelled 9.5 kWh battery and 4 kWp of panels, on the prices Octopus published and the sun that came, planned on the forecasts as issued, 1 October 2025 to 30 September 2026. How Orza is tested.
Planning pays in summer when export is paid by the hour.
In summer these panels made about 1.7 times what the house used, so there is sun to spare almost every day. What decides whether planning helps is what that spare sun is worth, and when.
Saved over May to August, average home: left to itself, then planned
- Flux: £76.01, planned £179.35£103.34 more. Flux pays most for export from 4pm to 7pm, so sun held back for those hours earns more than sun sold at midday.
- Agile with Agile Outgoing: £82.98, planned £136.29£53.31 more. Agile Outgoing pays least at midday and most in the evening.
- Agile with Outgoing Octopus: £71.49, planned £105.53£34.04 more, on a flat export rate.
- Go, nothing paid for export: £151.28, planned £159.04£7.76 more. With export worth nothing, storing every spare kWh is already the right answer.
- Agile, nothing paid for export: £152.00, planned £155.91£3.91 more, for the same reason.
Orza decides, every half hour, whether your sun is worth more stored or sold.
Free, with no card: an email and a password, and you look round an example home first. Connect your battery through its maker’s cloud when you’re ready, or never. It starts in Monitor only, and nothing is sent to it until you choose.
On Flux, planning was worth the same every summer month.
What the battery saved each month against the same home with no battery: left to itself, then planned by Orza.
| Month | Flux | Agile with Agile Outgoing | Agile with Outgoing Octopus | Go, nothing for export |
|---|---|---|---|---|
| May 2026 | £21.29, £44.39 | £18.32, £24.68 | £15.78, £16.26 | £42.23, £44.42 |
| June | £17.61, £43.08 | £19.47, £37.27 | £14.61, £30.26 | £36.04, £38.21 |
| July | £17.30, £46.26 | £19.23, £36.22 | £15.60, £29.21 | £33.89, £35.64 |
| August | £19.81, £45.62 | £25.96, £38.12 | £25.50, £29.80 | £39.12, £40.77 |
Each cell is left to itself, then planned. The average of 20 homes with a 9.5 kWh battery and 4 kWp of panels facing south, May to August 2026. Saved is against the same home, panels and tariff with no battery. Standing charges are left out, and no limit was put on export.
- Flux: £43 to £46 planned every monthAgainst £17 to £21 left to itself. The evening export price is there every day, so the gain is too.
- Agile with Outgoing Octopus: May was almost a tie48p apart in May, then £14 to £16 a month apart in June and July.
- With a bigger battery and roof, the gap grew13.5 kWh and 6 kWp on Flux: £75.72 left to itself, £251.85 planned, May to August.
In summer, only on the days it pays.
Most summer days the sun fills the battery anyway, so a charge from the grid only takes room the sun would have used. The planned figures above include filling from the grid wherever it paid, and on the tariffs with nothing paid for export, that added little. There are days it pays, though.
When a summer grid charge is worth it
- When Agile goes below zeroMostly in the middle of the day from April to October. A battery with room is paid to fill. How often, and what to do.
- Before a dull dayWhen the forecast says the sun won’t fill the battery, the cheap hours before it can. What a better forecast is worth.
- On Flux, to sell in the eveningIts cheapest hours are 2am to 5am and it pays most for export from 4pm to 7pm, so a planned battery has two prices to work with every day.
Before you leave it on self use for the summer.
What changes the answer for your home.
All our guidesGet more from your battery
How Orza is tested
Should I charge my solar battery from the grid in summer?
Only on the days it pays: when Agile goes below zero, before a dull day, or on Flux to sell at the evening price. Most summer days the sun fills it. With nothing paid for export, planning, grid charging included, added only £3.91 to £7.76 over May to August.
Is self use mode fine in summer?
If you are paid nothing for export, very nearly: planning added £3.91 to £7.76 over the four months. If export is paid by the hour, self use sells spare sun as it comes, around midday, when Agile Outgoing pays least and Flux pays less than its evening rate.
Does my export tariff matter more than my battery in summer?
It decides what the battery’s spare sun is worth. How Agile Outgoing and Outgoing Octopus compared for one real home, and when storing beats selling.
Does an export limit change this?
It can. These homes had no limit on export. A limit caps how fast a battery can sell in the evening and how much midday sun can leave the house. What an export limit cost one home.
What does Orza cost?
Nothing right now: everything is free while we spread the word, and no card is needed to join. Paid tiers will come later, and there will always be a free version.
Stored or sold, decided every half hour, all summer.
Free, with no card. Look round an example home first, and connect your battery when you’re ready.