The story this week: Ofgem steps in after June’s extreme heat stressed the electricity system
Ofgem has announced a formal review and an independent investigation into how the UK’s electricity system was operated during June’s extreme heat event. The regulator has commissioned NESO (National Energy System Operator) to produce a post‑event analysis covering the weather conditions, how the system was run, and how key decisions were made. Separately, Ofgem is also overseeing matters linked to whistleblowing allegations about NESO’s conduct during the event.
That might sound like distant, national‑level news. But for homeowners in places like Bordon, Whitehill, Liphook, Alton, Farnham and Haslemere, it points to something very practical: the UK’s energy system is being pushed harder in summer than it used to be. That changes how we should think about heating, hot water, heat pumps, smart tariffs, and home resilience generally.
What actually happened (in plain English)
During the June heat, the electricity system had to cope with conditions that are becoming more common: prolonged high temperatures, higher daytime demand (especially from cooling, refrigeration, and workplaces), and constraints on parts of the infrastructure that were designed for a different climate pattern.
Ofgem’s move signals two things:
- This mattered enough to trigger formal regulatory scrutiny, not just an internal “lessons learned”.
- System operation during extreme heat is now being treated as a consumer issue—because if the grid is strained, households can face higher costs, disrupted service, or new rules around demand management.
Even if you personally didn’t notice any disruption in Hampshire or the Surrey borders, the investigation is about how close the system came to trouble, and whether operational decisions were appropriate. The outputs can influence future guidance on how the grid is managed in heatwaves—right down to how household devices are encouraged (or incentivised) to run.
Why this matters to homeowners (it’s not just a “power industry” story)
Historically, most households worried about energy resilience in winter: frozen condensate pipes, boiler breakdowns, high gas bills. But the UK is now living with a different pattern:
- Hotter summers that push electricity usage up.
- More electrification (heat pumps, EV charging, induction cooking).
- More “smart” control (time‑of‑use tariffs, automated load shifting).
As more heating and hot water becomes electrically driven, the way the grid performs on the hottest days starts to affect your comfort and running costs just as much as what happens on the coldest nights.
In practical terms for homes in Farnham and Haslemere with larger properties and home offices, or newer developments around Bordon/Whitehill where electrification is more common, peak summer electricity demand can translate into:
- Greater price volatility on flexible tariffs.
- More calls to shift usage (e.g., running hot water or charging EVs at different times).
- More attention on “demand” devices like heat pumps, immersion heaters, and battery systems.
The technical bit: how extreme heat changes grid performance
It’s tempting to think: “Heatwaves mean less heating, so surely energy demand falls.” In reality, heatwaves can put the electricity system under strain for several engineering reasons:
1) Power cables and lines carry less safely in high temperatures
Overhead lines sag more when they get hot. Underground cables and transformers have thermal limits too. When ambient temperatures are high, the system sometimes has to run equipment with more caution, which can reduce the effective capacity available at peak times.
2) Some generation performs less efficiently
Heat can reduce the efficiency of certain power stations, and maintenance schedules can coincide with summer. Not every part of the generation fleet is equally comfortable in prolonged high temperatures.
3) Demand patterns change sharply
Air conditioning is not as widespread in UK homes as in hotter countries, but it is growing in workplaces, server rooms, retail, and newer domestic installs. Add to that increased use of fans, refrigeration working harder, and people at home using more appliances during heat stress. The result is a different peak demand profile—often peaking later in the day than traditional winter peaks.
4) Electrified heating still matters in summer because of hot water
If you have a heat pump or an electric cylinder/immersion for hot water, you still have an electrical load even when you’re not “heating the house”. On very hot days, some systems will also work harder to keep cylinder temperatures stable and safe (particularly if you’re using hot water more frequently due to showers).
5) Smart control becomes part of system operation
The modern grid increasingly relies on demand response—encouraging loads to move away from stressed periods. Ofgem’s focus on decision‑making during the heat event hints that operational choices (not just the weather) can affect outcomes. That matters because many households now have devices designed to respond automatically: smart thermostats, heat pump controllers, EV chargers, and battery inverters.
What it means technically for home heating and hot water
For most homeowners, the immediate question is: “Will my boiler or heat pump be affected?” The answer depends on your system.
If you have a gas boiler
A gas boiler is not directly dependent on grid capacity to produce heat, but it does rely on electricity for controls, ignition, pumps and fans. If there’s a power cut, your boiler will not run. The Ofgem review is not predicting outages; it’s investigating system operation. However, it underlines why it’s sensible to think about short power interruptions and what they mean for:
- Hot water availability (no electrics = no boiler operation).
- Heating controls (smart thermostats, internet hubs, and zone valves may not behave as you expect after an interruption).
In towns like Alton and Liphook where many properties are still gas‑heated, a heatwave grid issue won’t raise heating demand, but it can still impact hot water continuity and appliance behaviour.
If you have a heat pump
Heat pumps are fully dependent on electricity, and their running costs can be more sensitive to time-of-use pricing. During stressed grid periods, you may see:
- Higher peak prices on agile tariffs.
- More incentive to pre-heat hot water earlier in the day (while staying within safe temperatures and manufacturer guidance).
- Potential utility “events” asking customers to avoid discretionary use at certain times.
Technically, a heat pump also has operating limits in high ambient temperatures—though in summer it’s normally only producing hot water. If your unit is installed in a tight, sun‑baked location (a south‑facing corner with poor airflow is a common culprit), extreme heat can reduce performance and may trigger protective behaviour. That is an installation/detail issue we can usually improve: shading, clearance, air circulation, and correct siting.
If you rely on an immersion heater for hot water
An immersion heater is simple but expensive to run at peak rates. If system stress in heatwaves pushes prices up, the “hidden” cost of that cylinder can jump. Many homes in the area—especially older properties in Haslemere or rural edges around Farnham—have cylinders where the immersion has become the default due to a failed programmer, a broken boiler control, or a miswired hot water zone. That’s easy to miss because it still “works”, just at a much higher cost.
What it means financially: bills, tariffs and the cost of doing nothing
Ofgem’s investigation isn’t a new charge on your bill. The financial relevance is more indirect—but very real:
1) Peak pricing exposure is becoming a bigger deal
If you’re on a smart tariff that tracks wholesale conditions, stressed periods can mean higher electricity costs. Heat pumps, immersion heaters, and EV chargers can magnify that. A household in Whitehill with a heat pump and an EV could see “coincidental load” (hot water + charging + cooking) landing right in an expensive window unless it’s actively managed.
2) Energy resilience improvements may become better value
As the grid leans more on demand flexibility, investments like better hot water insulation, properly set cylinder schedules, and smart controls that are configured correctly become more worthwhile. These are not glamorous upgrades, but they can materially reduce your exposure to peaks.
3) Poorly set systems cost more in summer than most people realise
We often find summer running costs caused by:
- Cylinders maintained at unnecessarily high temperatures all day.
- Immersion heaters left permanently on.
- Heat pumps cycling due to incorrect hot water settings.
- Timers wiping their programmes after brief power interruptions.
Heatwaves don’t cause those faults, but they make the cost of them more painful—especially if prices are peaky.
Local relevance: what households in Bordon, Whitehill, Liphook, Alton, Farnham and Haslemere should watch for
National grid events land locally in different ways. In our patch, there are a few patterns worth noting:
- Mixed housing stock: From period properties around Farnham and Haslemere to newer housing around Bordon/Whitehill. That means a wide spread of system types—combis, system boilers with cylinders, heat pumps, and hybrid setups.
- Longer hot water pipe runs in larger homes: Bigger properties can have higher hot water losses, so poorly insulated pipework quietly drives up summer energy use.
- Home working: In areas like Liphook and Alton, daytime occupancy is often higher than it used to be. That changes when hot water demand happens, and it can clash with peak electricity periods.
The Ofgem review is essentially a warning light that “summer peaks” are now important. Even if your heating is off, your home is still an energy system.
What homeowners should do next (practical steps that actually help)
Check what heats your hot water today
Find out whether your hot water is being made by: boiler, heat pump, immersion heater, or a mix. If you have a cylinder, confirm whether the immersion is on a timer or permanently energised. A surprising number of households are unintentionally using immersion as the primary heat source.
Review your hot water schedule and cylinder temperature
For most homes, you don’t need all‑day hot water heating. A timed heat period (or two shorter periods) is usually enough. Keep temperature settings within manufacturer guidance and safety requirements—hot water must be stored hot enough to control legionella risk, but it also shouldn’t be running higher or longer than necessary.
Make sure your controls recover properly after a brief power cut
If your programmer loses time or settings when power is interrupted, you can end up with heating/hot water running at odd times. If you’ve noticed the clock drifting, displays flashing, or schedules “forgetting”, it’s worth sorting now—these small faults translate into real money on modern tariffs.
Heat pump owners: check airflow, siting and summer hot water behaviour
Look at where the outdoor unit sits. Is it in full sun with limited clearance? Are leaves/debris restricting airflow? Does it short‑cycle when making hot water? These issues don’t always break the system, but they affect efficiency and reliability during extremes.
Consider surge protection and sensible electrics for plant rooms
As homes add controls, Wi‑Fi thermostats, smart relays and motorised valves, they become more sensitive to electrical disturbances. A qualified electrician can advise on protection where appropriate. It’s not about panic; it’s about recognising that more of your comfort now depends on electronics.
If you’re considering a heat pump, design for both winter cold and summer heat
Heat pump conversations too often focus only on “can it heat the house in January?” A good design also anticipates:
- How hot water will be made efficiently year‑round.
- How the system will run on flexible tariffs.
- Where the outdoor unit will sit to avoid heat stress and noise issues.
That’s particularly relevant for homeowners planning upgrades in Bordon and Whitehill, where property improvement and electrification are common topics.
What to expect next from Ofgem’s review (and how to stay ahead)
Ofgem’s process is aimed at establishing facts, learning lessons, and strengthening resilience. For households, the likely downstream effects over time are:
- More emphasis on demand flexibility and smart usage during stressed periods.
- Greater scrutiny of operator decision‑making, which can shape future operational rules.
- Potential consumer guidance around participation in flexibility schemes and protections where automated control is involved.
You don’t need to wait for the final report to benefit. The best “homeowner response” is to treat hot water and heating controls as an engineered system, not just a set-and-forget utility. A quick audit of what you’ve got—what heats the water, when it runs, and whether it’s behaving as intended—can cut waste and reduce your exposure to peak prices, regardless of what the grid does next.
Need a proper check of your hot water controls, immersion setup, heat pump settings or overall system efficiency? Book with Embassy Gas: https://www.embassygas.com/book | (01420) 558993 | helpdesk@embassygas.com