Solar panels on UK homes produced enough electricity to run air conditioning for five hours each day during last month’s heatwave. That figure, from energy think tank Ember, is the first time the overlap between generation and cooling demand has been quantified at a household level, as reported by Ember Energy.
Why the timing matters for your bills
Air conditioning units draw 1–2 kW per hour of running time. A typical 3.5 kW solar system generates 15–20 kWh on a sunny July day. That is enough to cover five hours of midday cooling without drawing from the grid. For a household running one portable unit at 1.5 kW, that saves roughly £1.80 per day at current price cap rates of 24.5p per kWh. Over a two-week heatwave, the saving hits £25, enough to offset a month’s standing charge.
The critical point is timing. Solar output peaks between 11am and 4pm, exactly when indoor temperatures peak and air con demand spikes. This is not a theoretical overlap, it is a practical one that reduces strain on the grid and puts money back in homeowners’ pockets. Ofgem’s latest data shows that households with solar export tariffs earn an additional 15p per kWh for surplus power, meaning those five hours of generation also produce income if the air con is off.
EPC ratings and the solar imperative
The government’s consultation on minimum EPC standards for owner-occupied homes is expected to set a C rating target by 2030. Solar panels currently add 5–10 points to an EPC score, often lifting a D-rated property into the C band. Heatwave performance data like this strengthens the case: solar provides winter insulation and summer demand reduction. The Energy Saving Trust estimates a typical 3.5 kW system costs £5,000–£6,500 installed and saves £270–£400 annually on electricity bills. With the 0% VAT rate extended to 2027, payback periods have shortened to 12–15 years for most homes.
But the catch is roof orientation and shading. South-facing roofs with no overshadowing generate 20% more than east-west arrays. Homeowners considering solar should commission a site survey before ordering. The Microgeneration Certification Scheme (MCS) database lists approved installers, a prerequisite for Smart Export Guarantee payments.
What this means for future-proofing your home
Heatwaves are becoming longer and more frequent. The Met Office’s 2023 State of the UK Climate report recorded 15% more cooling degree days than the 1991–2020 average. As summer electricity demand rises, solar self-consumption becomes an increasingly valuable hedge against price cap increases. Battery storage adds another layer: a 5 kWh battery can shift the afternoon solar surplus to evening air con use, eliminating grid draw entirely during heatwave days. Costs for lithium-ion batteries have fallen below £1,000 per kWh installed, with some suppliers offering finance packages.
Households on standard variable tariffs should check their smart meter data for July’s peak hours. If you saw high consumption between 11am and 4pm, solar with a battery could cut that to zero. The Smart Export Guarantee pays for any surplus, currently averaging 12p per kWh across suppliers. For a 3-bed semi with a 4 kW system, that adds £100–£150 a year in export income.
Action point: Check your EPC certificate for the ‘current’ and ‘potential’ scores. If a solar PV system is listed as a recommended measure, the payback calculation now includes summer air con savings. Speak to an MCS-accredited installer before the autumn, wait times for installations currently run 6–10 weeks. The next heatwave will arrive before you expect it.
Frequently Asked Questions
A typical 3.5 kW system costs £5,000–£6,500 installed, including 0% VAT. Prices vary by roof type, scaffolding, and inverter quality. Check the MCS database for accredited installers.
Solar panels generate power from diffuse light, not just direct sun. On overcast heatwave days, output drops to 10–20% of peak, still enough to run a fridge and lights. Battery storage helps bridge the gap.
