Britain’s solar fleet just banked an extra £40 million in a single heatwave. That is the rough value of the electricity generated above normal levels by the 1.2 million homes and businesses with panels, as the mercury climbed and the sun hammered down for days on end.
The figure comes from analysis by Trending Now Sustainable Construction, as reported by Trending Now Sustainable Construction. The estimate assumes average export rates and typical system sizes, and it underlines a simple truth: when the sun shines, solar owners earn. The rest of us pay peak prices for the grid electricity that solar displaces.
What it means for a typical 3-bed semi
For a household with a 4 kilowatt system facing south in, say, Milton Keynes, the heatwave period probably added £80–£120 to the value of electricity generated. That is not cash in hand, most of it is avoided import, saved at the current price cap rate of around 24.5p per kilowatt-hour. If you are on a Smart Export Guarantee tariff paying 15p per kWh, you might have seen an extra £30–£40 exported to the grid.
The catch: heatwaves also drive up cooling demand. Fans, fridges and air-conditioning units all pull more power. But solar generation peaks around 11am–3pm, exactly when indoor temperatures and cooling loads are highest. So the self-consumption match is unusually good, you are using your own electrons to keep cool, not buying them at peak rates from the grid.
Who qualifies, and who doesn’t
Every home with solar panels benefited, but not equally. East- and south-facing arrays with no shading will have performed best. West-facing systems, common on new-builds, still got strong afternoon generation but missed the very highest irradiance around midday. North-facing panels, rarely worth installing, would have seen only a marginal gain.
Renters and flats without roof access are locked out entirely. For them, the heatwave is just a hotter, more expensive week. Community solar schemes, where they exist, offer some exposure, but only about 3% of UK households are connected to one, according to Energy Saving Trust data.
What this does to your EPC
Solar panels alone can lift an Energy Performance Certificate from a D to a C, provided the rest of the fabric is reasonable. The heatwave generation is not recorded on the EPC, that is based on modelled annual output, but the installation itself adds up to 10 points to the rating. For a typical three-bed semi, that could mean moving from 55 (D) to 65 (C), which is the threshold many mortgage lenders now require for green products.
Ofgem does not track heatwave-specific generation, but National Grid ESO data shows solar output peaked at over 11 GW on the hottest days, nearly double the typical summer level. That is enough to power 3.5 million homes for an hour. The £40m bonus is a real, if lumpy, financial benefit that does not show up on any official statement.
What you should do now
If you already have solar, check your inverter app or smart meter data to see how much extra you generated. If you don’t, this heatwave is a data point for your payback calculation. A typical 4kW system costs £5,000–£6,500 installed and, based on current prices, pays back in 8–12 years. A single heatwave like this one shaves a few weeks off that timeline.
The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing. But the Smart Export Guarantee is mandatory for suppliers with over 150,000 customers, you will get paid for every kWh you export. Octopus Energy, EDF and E.ON all offer tariffs at 15p/kWh or better. Apply through your supplier’s website. Most installations take one to two days. The next heatwave is not guaranteed, but the sun is.
Frequently Asked Questions
A typical 4kW south-facing system likely generated £80–£120 more in avoided electricity costs, plus £30–£40 in export payments if on a Smart Export Guarantee tariff. Exact figures depend on shading, orientation, and your tariff rate.
No, the EPC is based on modelled annual generation, not weather events. But installing solar panels can add up to 10 points to your rating, often moving a D-rated home to a C.
