Ofgem’s Heatwave Probe: What It Means for Your Home

The UK’s electricity grid buckled under the 2025 heatwave, transformers failed in three regions, voltage dropped by 8% in parts of the South East, and National Grid issued two emergency notices. That is the backdrop to Ofgem’s decision to commission an independent review of heatwave operations, as reported by Global Banking & Finance Review. For the 27 million households who rely on that grid to keep lights on, food cold, and fans spinning, this is not a technical footnote. It is a signal that the system designed for a mild climate is no longer fit for purpose.

What the review will actually examine

Ofgem has asked the review panel to look at three things: how network operators communicated during the heatwave, whether emergency protocols worked, and what physical infrastructure failed. The regulator has not yet named the panel chair or published terms of reference. But the scope matters because it will determine whether the outcome is a new set of compliance forms or real investment in grid hardening.

Documents seen by the Energy Systems Catapult suggest that distribution network operators underspent by £340m on heat-resilience upgrades over the past five years. If the review finds that underspending contributed to the failures, Ofgem could force operators to accelerate the next price control round, RIIO-ED3, which starts in 2028. That means higher network charges for households, but also fewer blackouts during heatwaves.

What a hotter grid means for your energy bill

The immediate cost of heatwaves is already visible. During the July 2025 heatwave, day-ahead wholesale electricity prices hit £285 per MWh, 40% higher than the same week in 2024. Those costs feed directly into the price cap, which Ofgem updates every quarter. The cap for October 2025 is set to rise by £63 to £1,823 for a typical dual-fuel household, partly driven by summer price spikes.

But the bigger cost is unmeasured: the number of households that bought portable air conditioning units in 2025 jumped 60% year-on-year, according to Currys sales data. Running one for 8 hours a day costs about £1.50 at current capped rates, £45 a month added to the electricity bill. For the 4 million UK homes with no insulation above 100mm in the loft, much of that cooling is wasted.

The catch is that the review will not directly lower those costs. It will produce recommendations, likely in early 2026, that Ofgem may or may not adopt. Homeowners cannot wait that long.

Who qualifies for cooling support, and who doesn’t

The government’s Cold Weather Payment scheme only triggers below 0°C. There is no equivalent for heatwaves. The Warm Home Discount, worth £150, helps with winter bills but does not cover summer cooling. The Energy Company Obligation (ECO4) can fund insulation and heat pumps, but not air conditioning units or fans.

That leaves households to fend for themselves. The cheapest intervention is draught-proofing windows and doors, roughly £200 for a typical 3-bed semi, saving up to £45 a year on heating and cooling combined, according to the Energy Saving Trust. The next step is loft insulation top-up: £300-£400, saving £35-£50 a year. Neither is glamorous, but both work in winter and summer.

For those considering a heat pump, the Boiler Upgrade Scheme offers £7,500 off installation. Heat pumps also provide cooling in reverse cycle, though most UK installs are not configured for that. Ask specifically for a reversible model, it adds roughly £500 to the install cost but eliminates the need for a separate AC unit.

What to do now, before the next heatwave

The review will take months. The next heatwave could come in weeks. Households on standard variable tariffs should check whether their supplier offers a time-of-use tariff, Octopus Agile, for example, charges negative prices during windy nights but spikes during peak demand. Shifting cooling to early morning or late evening can halve the running cost.

Anyone considering solar panels should know that summer generation peaks at the same time as cooling demand, a 4kW system can offset the full load of a portable AC unit during daylight hours. The Smart Export Guarantee pays 15p per kWh exported, but self-consumption avoids the 25p/kWh import cost entirely.

Ofgem’s review is necessary. But it is a process, not a solution. The solution is in the home: better insulation, smarter usage, and equipment that works both ways. Homeowners who act before the next heatwave will pay less, stay cooler, and be less exposed to whatever the review recommends, or fails to recommend.