Rooftop solar – the big one.
Panels, a roof, and about £6,500. Done right, the cheapest electricity you'll ever buy. Done wrong, a very expensive way to impress the neighbours.
An MCS-certified installer puts eight to ten panels on your roof. The fitting itself takes a day or two – but the whole affair runs longer: a survey, a scaffolding lorry, the install, the electrician, then the paperwork. Allow a few weeks from deposit to switch-on, and treat anyone promising it all by Friday with suspicion. The panels are warrantied for around 25 years. The inverter – the box that turns their output into household electricity – is not, and usually wants replacing around year 12 for about £800. Budget for it now and it's maintenance. Discover it in year 12 and it's a betrayal.
Two bits of officialdom, both smaller than they sound. Planning: most homes don't need permission – rooftop solar counts as 'permitted development' – unless the building is listed or you're in a conservation area, in which case ring the council before the scaffolding does. The grid: your installer notifies your local network operator – the people who own the wires, not the people who send your bill. For a normal-sized system that's a form sent after the switch-on; for a big one it needs sign-off first. Either way, it's the installer's job. If they try to make it yours, find a better installer.
Two ways. First: every unit you use yourself is a unit you don't buy at full price – about 26p as we write. Second: whatever you don't use is sold to your supplier for rather less. And there's the rub. A typical household only uses a fifth to a third of what its roof makes, because the roof does its best work at noon and you're at work. The rest goes out at the export rate, and the gap between a lazy export tariff and a good one is the difference between payback in 12 years and payback in 17. It's why our quiz asks whether anyone's home during the day. Installers rarely ask. It doesn't help the brochure.
Semi-detached, south roof, average region, 2,500 kWh a year (the Ofgem typical value)
Import 26.11p/kWh (Ofgem cap Jul-Sep 2026). Export shown as a pair: 6p no-switch / 12p strong switchable. Constants v0.5.3, 2026-08-27.
Oddly, yes. The more you use, the more of the roof's output you soak up at full value, and the bigger the system that makes sense in the first place. Solar is one of the few corners of life where being a heavy user counts in your favour. Enjoy it.
Homeowners with a roof pointing anywhere from east round to west, planning to stay put long enough for the maths to finish. Leaseholders: freeholder consent is a real hurdle, not a formality. Renters and flats: not this route – but keep reading, because two of the other three were built with you in mind.
There's no grant, and there never really was one worth the name. What exists: panels are already VAT-free, and VAT on electricity drops to 0% from 1 October 2026. Real, but modest. And if you move before payback finishes, the panels stay with the house – they'll add something to the asking price, but nobody has ever got their money back at the removal van.
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