Every price cap rise quietly rewrites the payback maths on plug-in solar, and July's was a big one: the capped electricity rate is now 26.11p/kWh, up from 24.67p in the spring. Time to rerun the numbers.
The simple version
A plug-in kit doesn't earn money; it stops you spending it. Every kWh your panels generate and you use is a kWh you don't buy at the capped rate. So the value of a kit's output rises in lockstep with electricity prices — no paperwork required.
An 800W kit in a reasonable UK position generates roughly 600–750 kWh a year. At 24.67p, self-consuming most of that was worth £120–£160 a year. At 26.11p it's £130–£175. The kit didn't change. The grid got more expensive around it.
Payback periods, August 2026 edition
Take the two kits we recommend most. The Anker SOLIX RS40P at £419–£449: payback now lands around 2.7–3.4 years for a well-sited install with decent daytime self-consumption. The EcoFlow STREAM 800W at £499: around 3–3.8 years, with the battery-ready architecture as the tiebreaker.
Panels are warrantied for 25 years. Even our pessimistic scenarios — shading, low self-consumption, a mild summer — struggle to push payback past six. The remaining nineteen years are, in technical terms, free electricity.
The caveat we always give
These numbers assume you use the power as it's generated. Export without an agreement earns nothing, so daytime self-consumption is the whole game: run the dishwasher at noon, not midnight — unless you're on a smart tariff, where midnight might win anyway.
Which is why the pairing matters. On Octopus Agile, cheap or negative midday pricing plus solar generation stack rather than compete — our full analysis here. Switch via our referral link and there's £50 credit on each side of the arrangement.
The October cap announcement lands 26 August. If it rises again, this article's numbers become conservative. We can live with that.
