Solar plus a battery – three ways to gain.
A suitcase-sized box that stops you giving your solar away. It costs as much as a decent used car, which is why it deserves a colder look than it usually gets.
The same install as rooftop solar, plus a battery on the wall – usually 5 to 10kWh, about half a day extra on the job. It catches the lunchtime solar you'd otherwise sell for pennies and hands it back in the evening, when you'd otherwise be buying at 26. On the right tariff it also fills itself with cheap overnight electricity. Expect 10 to 15 years from it – it will very likely retire before your panels do.
Three ways. One: you now use most of your own solar instead of a fifth of it. Two: export income on what's left. Three: cheap overnight charging – buy at the night rate, use at the day rate, pocket the spread. That third one carries a condition: it only exists on a time-of-use tariff. Several suppliers offer them, you may well need to switch to get one, and the switch is part of the deal. If you won't switch, buy the battery expecting two income streams, not three – it changes the maths, and not in your favour. Nobody pays us to say any of this. No supplier, no installer, nobody.
Semi-detached, south roof, average region, 2,500 kWh a year (the Ofgem typical value)
Import 26.11p/kWh (Ofgem cap Jul-Sep 2026, GB average direct debit, including VAT at 5%). Export shown as a pair: 6p if you do not switch supplier, 12p if you do. Export rates are supplier-set, not regulated, and the underlying data covers April 2024 to March 2025 – Ofgem Smart Export Guarantee Annual Report, Year 5 (published December 2025). Constants v0.6.0, 2026-09-19.
Very much so. Heavy users, EV owners, heat pump homes: the battery was practically designed for you. The more electricity your evenings drink, the harder the box on the wall works – and the quicker it justifies itself.
Bigger electricity users, EV owners, heat pump homes, and anyone regularly out during the day – the battery fixes exactly the problem daytime absence creates. We show the battery's own payback separately on your result, because panels and battery bundled into one number is how a weak battery case hides inside a strong solar one. It's the oldest trick in the brochure.
The battery will probably need replacing before the panels do – put it in the sums. And the eye-catching export rates you may have read about are tied deals – they pay that much only if you buy your electricity from the same company, and they come with conditions. Rates that pay you whatever you buy from cluster far lower. Anyone quoting a single typical export rate is quoting the wrong number.
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