The Environmental Cost of Keeping Cool

If Britain Embraces Air Conditioning, Can We Do It Without Creating a New Energy Problem?

“The question is no longer whether British homes will need cooling. It is how intelligently we choose to provide it.”

For most of my life, the British house has been designed around one overriding problem: how do we keep warm?

We fitted double glazing. We filled cavity walls. We piled insulation into lofts. We sealed draughts. We installed better heating controls.

All perfectly sensible.

But our climate is changing the design problem.

Increasingly, there are days when the problem is not keeping heat inside the house but desperately trying to get it out again. In England, around 3 million homes were reported as getting uncomfortably hot in 2024, and the proportion reporting overheating has risen from 7% in 2019 to 12% in 2024.

The Climate Change Committee warns that, by the middle of the century, as many as 92% of existing UK homes could experience overheating under future conditions.

So perhaps it is inevitable that more of us will start looking at the white box on the wall familiar in Spain, Greece, Italy and much of the United States and asking:

Should I have air conditioning?

There is nothing inherently wrong with that question.

Air conditioning can make dangerously hot rooms comfortable. It can help people sleep. It can protect vulnerable people. It can make working from home possible during a severe heatwave.

Indeed, recent Climate Change Committee work includes active cooling as part of a cost-effective adaptation package for particularly vulnerable areas, alongside ventilation, shading and insulation.

The problem comes if our national response to hotter summers becomes simply:

“It's hot. Buy an air conditioner.”

Because if millions of us do that, we potentially create an entirely new energy problem.

Britain Could Develop a Summer Peak as Well as a Winter Peak

Traditionally, Britain's electricity system has had its greatest challenges during winter.

Cold weather means heating, darker evenings mean lighting, and household electricity demand rises just as solar generation falls.

Summer has often been easier.

But widespread mechanical cooling changes that equation.

Imagine, purely as an illustration, that five million homes eventually had cooling systems drawing an average of 1 kW while operating.

If they all happened to be running at the same time:

5,000,000 x 1 kW = 5 GW

That is 5 gigawatts of additional electricity demand.

Ten million homes would make the theoretical simultaneous load 10 GW.

That isn't a forecast; real equipment loads and operating patterns would vary enormously. But it demonstrates why millions of individually modest appliances can become a significant national infrastructure issue.

And this is not entirely theoretical anymore.

During extreme heat in June 2026, Britain's National Energy System Operator reported high sustained demand combined with low wind, reduced gas-generation availability, adverse interconnector flows and other constraints, producing tight operating margins. No customers were disconnected, but it demonstrated that summer electricity conditions can become challenging too.

The government itself now expects cooling demand to increase as temperatures rise and recognises that active cooling could add pressure to the electricity system.

So the environmental question is not simply:

How much electricity does my air conditioner use?

It is also:

What happens when several million other people switch theirs on at the same time?

The Cheapest Cooling Machine May Already Be in Your House

Before reaching for refrigeration, there is a remarkably effective piece of cooling technology available for £20 or £30.

The electric fan.

A fan does not significantly reduce the temperature of a room. Instead, moving air increases evaporation from our skin and makes us feel cooler.

That distinction matters.

Sometimes we don't actually need to cool 50 cubic metres of air.

We need to cool one person sitting at a desk.

Energy Saving Trust estimates typical 24-hour running costs in Great Britain of roughly:

Cooling method	Typical cost for 24 hours
Fan	£0.14–£0.30
Evaporative cooler	£0.27–£0.39
Portable air conditioner	£4.62–£5.00

These figures assume continuous use, but the difference is striking.

Run them continuously for a seven-day heatwave and that becomes approximately:

Fan: £0.98–£2.10
Portable air conditioner: £32.34–£35.00

There are obviously conditions where the air conditioner achieves something the fan cannot.

But that is precisely why we should choose the technology according to the problem.

If you are comfortable with a fan, turning an entire room into a refrigerator is unnecessary.

The Best Kilowatt of Cooling Is the One You Never Needed

There is another important principle.

Stopping a house becoming hot is usually much easier than cooling it afterwards.

Imagine sunlight pouring through a large south- or west-facing window.

The sunlight enters through the glass and is absorbed by floors, furniture, walls and carpets.

Those surfaces become warm and re-radiate the energy inside the room.

By 5pm, you may have several tonnes of warm building fabric that now needs cooling.

At that point the air conditioner has a considerable job to do.

Put an awning outside the same window, however, and much of that solar energy never enters the building.

That is a fundamentally different approach.

Instead of removing unwanted heat, we prevent the heat arriving in the first place.

External Shading Could Become the British Home's Next Big Upgrade

We are very familiar with curtains.

But curtains are inside the glass.

By the time sunlight reaches the curtain, much of its energy has already entered the building.

External shading intercepts it first.

That could mean:

awnings
external blinds
shutters
pergolas
brise-soleil
shade sails
trees
carefully positioned planting.

A retractable awning is particularly interesting for Britain.

In August it can shade the window.

In January it can be retracted, allowing valuable winter sunlight into the room.

That is exactly the sort of dual-climate design we increasingly need.

The British house of the future cannot simply be designed to keep heat in.

It must be capable of deciding when heat is welcome and when it is not.

Insulation Still Matters in Summer

It can initially seem contradictory.

Surely insulation makes an overheating house worse by trapping heat inside?

Not necessarily.

Insulation slows heat transfer in both directions.

A well-insulated roof can reduce the amount of heat entering from a roof surface baking in the summer sunshine, just as it reduces heat escaping through that roof during winter.

Energy Saving Trust therefore includes improved insulation among measures that can help keep homes cooler.

But there is an important qualification.

Insulation cannot work alone.

Once heat has entered a highly insulated house—from sunlight, cooking, computers, occupants or appliances—it may indeed remain there.

So insulation needs partners:

Insulation + shading + controlled ventilation.

It is the combination that matters.

Windows Open or Windows Closed?

This is one of the simplest cooling mistakes we can make.

Imagine:

Inside temperature: 24°C
Outside temperature: 32°C

Opening every window feels instinctively sensible.

But unless enough air movement is providing a useful cooling effect on you, you are effectively inviting 32°C air into a 24°C house.

Instead, during the hottest part of the day, it can be better to keep direct sunlight out and the hotter outside air outside.

Then suppose at 11pm:

Inside: 27°C
Outside: 19°C

Now open the house.

Use windows on opposite sides to create cross-ventilation.

Open upstairs windows where safe to exploit rising warm air.

A fan in a suitable position can help move cooler air through.

Daytime: defend the house from heat.
Night-time: purge the heat accumulated during the day.

That approach is also reflected in Energy Saving Trust guidance.

Perhaps We Should Cool People Before We Cool Buildings

There is an interesting psychological difference between heating and cooling.

During winter we don't usually expect every part of a house to be 25°C.

Yet air conditioning can tempt us into cooling entire spaces regardless of whether anyone is using them.

Suppose you are working in one bedroom office.

Do you need to cool:

the office,

the landing,

three empty bedrooms,

the kitchen,

and the lounge?

Probably not.

This suggests another principle for low-energy cooling:

Cool occupied spaces, not empty houses.

Smart-home technology could make a considerable difference here.

Presence sensors, room temperature sensors, automated blinds, smart fans and zoned air conditioning could all work together.

Instead of:

“Make the house 20°C.”

the instruction might effectively become:

“Keep occupied rooms comfortable using the lowest-energy method available.”

That is a much more intelligent control problem.

Air Conditioning Is Actually a Heat Pump

This is worth explaining because the terminology can become confusing.

An air conditioner does not really “make cold”.

It moves heat.

It collects thermal energy from inside the building and transfers it outside.

That is exactly what a heat pump does.

Reverse the cycle and many air-to-air systems can move heat from outside into the building during winter.

So one possible future is not:

boiler + separate air conditioner

but:

one reversible heat-pump system providing heating in winter and cooling in summer.

Energy Saving Trust specifically notes that air-to-air heat pumps can provide cooling and recommends considering passive cooling first before deciding how much mechanical cooling is required.

That integrated approach seems much more sensible than retrofitting increasingly large collections of independent appliances.

But What About My Existing Air-to-Water Heat Pump?

Here we need to be careful.

Many British heat-pump installations use hot water circulated through radiators.

That does not automatically mean you can simply put the system into reverse and pump cold water through ordinary radiators.

Cooling introduces other considerations, particularly condensation.

If pipework or emitters become colder than the dew point, water can condense onto them.

Systems designed for cooling may therefore use fan-coil units, suitable underfloor systems, condensation controls and appropriately insulated pipework.

So if you already own an air-source heat pump, don't simply assume that a hidden menu setting turns your central heating into air conditioning.

Cooling needs to have been properly designed into the system.

But when homes are being built or heating systems replaced, perhaps summer operation should increasingly become part of the design conversation from the beginning.

Then We Have the Perfect Coincidence: Solar Panels

There is one major difference between cooling electricity and winter heating electricity.

Cooling often happens when the sun is shining.

That could turn out to be extremely useful.

On 7 April 2026, Great Britain reached a new solar generation record of 14,414 MW between 12:30pm and 1pm.

If millions of homes eventually require cooling, using some of it when renewable generation is abundant could reduce its impact.

At home, having solar panels, battery storage and a heat pump has made me much more aware of when energy is available, rather than simply how much electricity we use over a day.

Cooling creates an interesting opportunity.

Instead of waiting until the house has become unbearably hot at 8pm and then demanding a large amount of grid electricity, a smart system might use excess solar generation earlier to stop the building temperature rising so far in the first place.

That doesn't mean making the house freezing cold at lunchtime.

It means perhaps holding it at 23–24°C rather than allowing it to rise to 29°C.

This is effectively using the building itself as a modest thermal store.

Solar Cooling Isn't Completely Free

It is tempting to say:

“I've got solar panels, therefore my air conditioning costs nothing.”

That isn't quite true.

Electricity used for cooling could otherwise have:

charged a battery
heated water
powered another appliance
been exported.

And solar panels themselves become slightly less efficient as their temperature rises.

Nevertheless, there is an extremely useful match between summer cooling demand and daytime solar production.

Battery storage could extend that advantage.

Solar generation during the afternoon could supply cooling directly while simultaneously charging a battery; stored electricity could then provide some cooling after sunset when the building is still releasing heat accumulated during the day.

That could become an important part of the smart home of the future.

The Environmental Cost Isn't Just Electricity

Air conditioning has another slightly ironic effect.

It cools the house by putting heat outside.

One individual outdoor unit is irrelevant to a street.

Hundreds or thousands operating in a densely populated urban area are different.

Research reviewed by government health advisers notes that waste heat from air conditioning can contribute to the urban heat island effect, potentially adding to outdoor overheating around buildings.

There is also the question of refrigerants.

Modern systems increasingly use refrigerants with lower climate impacts, but leakage still matters because some refrigerant gases can be powerful greenhouse gases.

Then there are the materials and energy involved in manufacturing millions of compressors, heat exchangers, fans and electronic control systems.

None of this means we shouldn't use cooling.

It means reducing the cooling load before installing the machine has environmental value twice over:

we consume less electricity and we can potentially install smaller equipment.

We Don't Need to Turn Britain Into a Refrigerator

Perhaps there is another cultural issue.

If it is 35°C outside, should we expect every house to be maintained at 18°C?

Probably not.

There is a large difference between:

comfortable cooling

and

aggressive refrigeration.

Each degree of unnecessary cooling requires additional work from the system.

Instead of asking:

“How cold can my air conditioner make the room?”

perhaps ask:

“What is the highest temperature at which I remain comfortably cool?”

A home maintained around 24–25°C with good air movement could feel perfectly pleasant while consuming considerably less energy than one being driven unnecessarily lower.

The One-Cool-Room Strategy

There may also be a very practical compromise for extreme heatwaves.

Instead of cooling the entire house, create one reliably cool room.

It might be:

a living room during the day
a bedroom overnight
a downstairs room that naturally remains cooler.

That room receives the best shading.

Its doors remain closed when mechanical cooling operates.

A fan improves air movement.

The air conditioner or heat pump only has to deal with one manageable volume.

Other rooms use passive measures.

Interestingly, the Climate Change Committee's recent adaptation work explicitly considered creating at least one cool room when temperatures rise as part of protecting vulnerable households.

For many homes, that may be far more realistic than trying to air-condition an entire British house that was never designed for it.

A Cooling Hierarchy for the British Home

Rather than deciding between air conditioning or no air conditioning, I would approach summer cooling in stages.

1. Stop sunlight entering

Use external shading where possible, then blinds and curtains.

2. Improve the building envelope

Insulate roofs and walls so outside heat enters more slowly.

3. Ventilate intelligently

Keep hotter outside air out during the hottest hours and purge accumulated heat when outside temperatures fall.

4. Reduce heat created indoors

Ovens, computers, tumble dryers, lighting and other appliances eventually turn most of the electricity they consume into heat.

5. Cool the person

Try a fan before refrigerating the entire room.

6. Cool the occupied room

Don't condition bedrooms, studies and lounges nobody is using.

7. Use efficient mechanical cooling

If air conditioning is required, correctly size it and operate it intelligently.

8. Integrate heating and cooling

Where appropriate, consider whether a reversible heat pump can perform both functions instead of installing entirely separate systems.

9. Match cooling with solar generation

Use abundant daytime renewable electricity where possible.

10. Use storage and smart controls

Batteries, temperature sensors, automated blinds and weather forecasts could eventually coordinate the whole system.

That isn't an anti-air-conditioning strategy.

It is an intelligent-air-conditioning strategy.

Try a Home Cooling Audit Before Buying Anything

A particularly useful experiment is to spend one hot week actually measuring what your house does.

You only need two or three inexpensive digital thermometers.

Record:

Time | Outside temperature | Lounge | Bedroom | Loft/landing

Then note:

which windows received direct sunlight
when curtains were closed
whether windows were open
whether a fan was operating
whether the oven was used
when temperatures peaked.

You may discover something surprising.

Perhaps the west-facing bedroom gains 5°C between 3pm and 7pm.

Perhaps closing one blind prevents most of it.

Perhaps opening windows at 2pm makes the house hotter, while opening them at 9pm drops the temperature quickly.

Perhaps the loft is transferring far more heat downstairs than you expected.

Only after understanding where the heat comes from can you make the best decision about how to remove it.

Air Conditioning May Sometimes Be the Green Choice

That sounds contradictory, but it needn't be.

Imagine two alternatives.

House A

Poor shading, large unprotected windows, portable air conditioner running continuously, windows leaking warm air around the exhaust hose.

House B

Good insulation, external shading, night ventilation, efficient reversible heat pump, rooftop solar, smart temperature controls and targeted cooling.

Both houses have mechanical cooling.

But their environmental impacts could be completely different.

Technology is not automatically green or ungreen.

How we integrate and operate it matters.

Britain Needs a Cooling Strategy Before Millions of Us Buy One Individually

This may be the larger lesson.

If hotter summers continue, households will not simply endure overheating because reducing electricity use is environmentally desirable.

People will buy cooling.

And quite reasonably so.

The question is whether we anticipate that change or allow millions of individual decisions to create a new national electricity peak.

Britain spent decades developing standards around insulation and winter heating efficiency.

Perhaps we now need the same seriousness about:

summer shading, overheating, ventilation and efficient cooling.

New homes should be designed for both January and August.

Existing homes should be adapted before overheating becomes intolerable.

Heat-pump installations should consider future cooling requirements.

Solar panels, batteries and smart controls should increasingly work together.

And perhaps external shutters and awnings will eventually become as normal on a British house as double glazing is today.

Conclusion: Cooling Is Going to Become Part of Going Green

I don't think the environmental answer is to tell people that they must simply tolerate increasingly uncomfortable houses.

Nor is it sensible to pretend that air conditioning is inherently environmentally irresponsible.

During severe heat, cooling may become an important part of keeping homes safe and usable.

But there is a huge difference between needing cooling and wasting cooling.

The green home of the future may well have air conditioning—or, more likely, a reversible heat pump capable of cooling.

But hopefully it will only need to use it after the house itself has done everything possible first.

The awning blocks the sun.

The insulation slows the heat.

The blinds close automatically.

The windows open when the evening air becomes cooler.

The fan keeps the occupant comfortable.

The solar panels provide the electricity.

The battery shifts some of it into the evening.

And only then does the compressor start.

Perhaps that is the future we should be aiming for.

Not a Britain without air conditioning.

A Britain that has learned not to waste it.