How Green Is Air Conditioning? The Real UK Carbon Cost

Air conditioning remains relatively unusual in British homes.

In the UK Government's Winter 2025 Public Attitudes Tracker, only 5% of households said they used air conditioning to cool their homes. By comparison, 80% opened windows or doors, 47% used plug-in fans, and 45% closed curtains or blinds. Air-conditioning use was reported by 6% of owner-occupiers and 3% of renters.

Commercial cooling is much more established.

A government study based on 2019 energy data estimated that UK non-domestic buildings used approximately 6.2 terawatt-hours of energy for cooling and humidification. Offices accounted for around half of that consumption, retail for approximately 19%, and healthcare for around 9% ( Energy Technology List, DESNZ).

Source: DESNZ / Energy Technology List, based on 2019 non-domestic energy data.

Globally, the scale is considerably larger. The International Energy Agency estimates that electricity demand for space cooling has grown by 50% since 2015, reaching around 2,900 TWh. That is more electricity than the entire European Union consumes across all uses. Cooling has accounted for approximately 14% of global electricity-demand growth over the same period.

Space cooling is now the fastest-growing source of energy demand in buildings and, under current policies, is expected to rise by almost 4% annually to 2035.

The carbon footprint of cooling will therefore become increasingly important, both globally and here in Britain.

The footprint can be divided into three broad areas:

• Electricity used during operation
• Refrigerant released through leaks or disposal
• Emissions from manufacturing, installation and end-of-life treatment

Electricity is the most visible element because it appears on energy bills. Refrigerants are less visible, but a relatively small leak can sometimes create a surprisingly large climate impact.

Manufacturing also matters. Air-conditioning systems contain steel, aluminium, copper, plastics, electronics and other materials that require energy to produce and transport. However, for equipment used frequently, operational electricity and refrigerant leakage will often be the most practical areas for households and businesses to measure and reduce.

There is no single figure that applies to every air conditioner.

Consumption depends on:

• the unit's electrical input
• its efficiency
• the size and temperature of the room
• insulation and glazing
• sunlight entering the building
• outside temperature and humidity
• the thermostat setting
• whether windows and doors remain closed
• and how long the compressor runs

A machine advertised as providing 3 kW of cooling does not necessarily consume 3 kW of electricity. Efficient air conditioners move several units of heat for every unit of electrical energy they use.

Nevertheless, a simple example can help communicate the scale.

Imagine a portable air conditioner averaging 1 kW of electricity consumption while operating for eight hours a day during a 30-day hot period.

It would consume:

1 kW × 8 hours × 30 days = 240 kWh

From July to September 2026, Ofgem's average capped domestic electricity rate for Direct Debit customers in England, Scotland and Wales is 26.11 pence per kWh. At that rate, the electricity would cost approximately:

240 kWh × £0.2611 = £62.66

The UK Government's 2026 company-reporting factors assign purchased UK electricity a location-based footprint of 0.13096 kg CO₂e per kWh. Transmission and distribution losses add approximately 0.01299 kg CO₂e per kWh, producing a combined illustrative figure of 0.14395 kg CO₂e.

The 30-day cooling period would therefore represent approximately:

240 kWh × 0.14395 kg CO₂e = 34.5 kg CO₂e

That is an illustration, not an average for every UK home. A highly efficient fixed system cooling one shaded room may use considerably less. A portable unit fighting solar heat in a poorly insulated loft room may use more.

The calculation also uses an annual average grid factor. The actual carbon intensity of electricity changes depending on the time of day, the weather and the mix of generation operating on the grid.

A typical plug-in or pedestal fan might consume around 50 watts, or 0.05 kW.

If it operated for the same eight hours a day over 30 days, it would use:

0.05 kW × 8 hours × 30 days = 12 kWh

At the same electricity price and emissions factor, this would cost approximately £3.13 and represent around 1.7 kg CO₂e.

Illustrative comparison based on 8 hours a day for 30 days, at Ofgem's July–September 2026 electricity cap (26.11p/kWh) and the UK Government's 2026 combined electricity + T&D emissions factor of 0.14395 kg CO₂e per kWh.

In this example, the air conditioner consumes approximately 20 times more electricity.

However, the comparison is not completely like for like.

A fan does not significantly reduce the temperature of a room. It moves air across the body, helping sweat evaporate and making people feel cooler. Air conditioning physically transfers heat outside and can also reduce humidity.

A fan may be sufficient during moderately warm weather. During severe heat, in an unsuitable building or for a medically vulnerable person, it may not provide the same protection.

The environmental lesson is not that fans and air conditioning are interchangeable. It is that personal cooling generally requires far less energy than cooling an entire room.

The words "air conditioner" can describe very different machines.

A portable single-hose unit, a modern fixed split system, a reversible heat pump and a large commercial chiller do not have the same efficiency or operating characteristics.

Government research into overheating concluded that fixed units could be three to four times more energy-efficient than portable air conditioners in some circumstances. Portable units must expel hot air through a hose, usually placed through a window or door opening. This can reduce their effectiveness and allow warm outside air to return to the room.

The Government's wider cooling study modelled a seasonal energy-efficiency ratio, or SEER, of approximately:

Source: DESNZ cooling modelling. SEER = Seasonal Energy Efficiency Ratio.

A higher SEER means that more cooling is delivered for each unit of electricity consumed. The figures are modelling assumptions rather than ratings for every product, but they illustrate the enormous difference equipment choice can make.

Portable units still have practical advantages. They are cheaper to buy, do not normally require permanent alterations and may be the only available option for renters.

But the lowest purchase price does not necessarily produce the lowest lifetime cost or carbon footprint.

The cheapest air conditioner to buy can become one of the most expensive to operate.

An air conditioner does not usually cool a room faster simply because the thermostat is set to an extremely low temperature.

Selecting 18°C instead of 24°C generally causes the compressor to operate for longer. It may also cool the room below the level required for comfort, increasing energy consumption without providing a proportionate benefit.

For offices, the UK Government's business energy-efficiency campaign recommends setting cooling at 24°C or higher, while adjusting operating times around actual staff and customer occupancy.

The most sustainable temperature is not the lowest one the machine can achieve. It is the highest setting that maintains a safe and comfortable environment for the people using the space.

Electricity is only part of the climate story.

Air conditioners contain refrigerants that absorb heat indoors and release it outside. Many existing systems use fluorinated gases, or F-gases, which can have a much greater warming effect than carbon dioxide if released into the atmosphere.

The UK Government's 2026 reporting factors assign:

• R32 a global-warming impact of 677 kg CO₂e per kilogram released
• R410A an impact of 1,924 kg CO₂e per kilogram released

These figures are used for UK greenhouse-gas reporting and may differ slightly from older values quoted online because reporting conventions and scientific assessments are periodically updated.

To understand the scale, consider a leak of only half a kilogram:

Refrigerant GWPs from the UK Government's 2026 greenhouse-gas reporting factors. Grid-electricity equivalence uses the combined electricity + transmission and distribution factor of 0.14395 kg CO₂e per kWh.

This does not mean every air conditioner releases its full refrigerant charge. A correctly installed, properly maintained sealed system should retain its refrigerant.

The risk comes from leaks, accidental damage, poor servicing and improper disposal. That is why installation quality and end-of-life refrigerant recovery are climate issues, not simply technical details.

Government guidance calculates refrigerant emissions by multiplying the quantity released by the refrigerant's global warming potential. For businesses, the amount added during servicing can provide evidence of how much refrigerant has been lost.

The industry is gradually moving away from some of the highest-impact refrigerants.

In Great Britain, movable air-conditioning equipment using F-gases with a global warming potential above 150 is already prohibited from being placed on the market. Since 2025, new small single-split systems containing less than 3 kg of refrigerant cannot use F-gases with a global warming potential above 750.

This has encouraged a transition away from R410A in many smaller systems. R32 has a lower warming impact, although it is still a greenhouse gas and must be contained and recovered responsibly.

Some portable systems use refrigerants such as R290, which is propane, a hydrocarbon rather than an F-gas. Its global warming potential is very low, roughly 3, which is why it is increasingly popular in smaller units. Because propane is flammable, product safety, installation and servicing requirements are stricter, and equipment using R290 should only be handled by qualified engineers.

A lower-impact refrigerant improves the picture, but it does not automatically make an inefficient air conditioner sustainable. The whole system must be considered, including electricity consumption, leakage, operating life and disposal.

For businesses, AC emissions can appear in several parts of a greenhouse-gas inventory:

• Scope 1: refrigerant leaking from equipment owned or controlled by the organisation
• Scope 2: purchased electricity used to operate the system
• Scope 3: emissions associated with electricity transmission and distribution, along with relevant supply-chain and equipment emissions

The Government publishes separate conversion factors so organisations can calculate and report these emissions consistently.

A simple commercial example

Imagine a business uses 10,000 kWh of electricity for air conditioning during the year.

Using the 2026 government factors, this would represent approximately:

Illustrative worked example only. Applies UK Government 2026 emissions factors and refrigerant GWPs.

In that scenario, one modest refrigerant loss would add almost two-thirds as much to the footprint as the entire 10,000 kWh of cooling electricity.

This is why a carbon audit that measures electricity but ignores refrigerant leakage can significantly underestimate the impact of commercial cooling. It is the same principle we set out in our guide to reducing a business carbon footprint: measure what you actually control before deciding what to reduce.

Government analysis indicates that offices account for around half of current non-domestic UK cooling demand, with retail representing the next largest share.

These buildings often contain several internal heat sources:

• computers and monitors
• lighting
• kitchen equipment
• refrigerators
• servers
• machinery
• employees and customers

Every watt of electricity used by equipment ultimately becomes heat inside the building. The cooling system must then remove part of that heat.

A computer therefore affects energy consumption twice: first through the electricity it uses directly, and then through the additional cooling required to remove the heat it releases.

Shop doors left open while AC is operating create another visible form of waste. The system continually cools incoming outdoor air, increasing both bills and emissions.

Deep-plan offices and shopping centres can be difficult to ventilate naturally, so mechanical cooling may be necessary. But necessity does not remove the opportunity for better controls, improved maintenance and lower cooling loads.

An air conditioner powered by low-carbon electricity will generally have a smaller operational footprint than the same system powered by a fossil-fuel-intensive grid.

On-site solar can be particularly useful for businesses because commercial cooling often peaks during sunny daytime hours. Domestic demand may peak later, when people return home and solar output is already falling.

A renewable electricity contract can also support an organisation's market-based Scope 2 reporting. However, UK environmental-reporting guidance still asks organisations to report location-based electricity emissions, with a market-based figure presented additionally where appropriate.

Even genuinely renewable electricity does not remove:

• refrigerant leakage
• equipment manufacturing
• installation impacts
• maintenance materials
• disposal
• or the pressure placed on the electricity network during periods of peak demand

Renewable power makes cooling cleaner. It does not make unnecessary energy consumption environmentally irrelevant.

The same honest logic applies here as it does to wind, solar and other lower-carbon sources: cleaner electricity is a big step forward, but it does not remove the responsibility to use less. Our companion piece on wind energy in the UK explores that point in more detail.

Air conditioning should not be the first response to every warm building.

Before installing or expanding mechanical cooling, households and businesses can reduce the amount of heat that enters or accumulates inside.

Measures can include:

• external shutters, awnings or solar shading
• closing blinds and curtains before direct sunlight enters
• solar-control glazing
• lighter-coloured roofs and external surfaces
• roof and wall insulation
• ventilation during cooler evening and morning periods
• reducing unnecessary lighting and equipment use
• planting trees and providing urban shade
• sealing openings around portable-unit exhaust hoses
• designing buildings for cross-ventilation

Insulation does not simply "trap heat". It slows heat transfer in both directions. It can reduce heat entering from outside, but a well-insulated building still needs shading and ventilation to prevent solar and internal heat from accumulating.

Government modelling suggests that passive-first strategies could substantially reduce future cooling-energy consumption and peak power demand. In a high-warming scenario, passive measures were estimated to reduce peak cooling demand by around 5.1 GW by 2100 compared with a no-intervention pathway.

That is equivalent to avoiding the simultaneous electricity demand of more than five million appliances drawing 1 kW each.

For a household that needs mechanical cooling, the greatest improvements usually come from reducing demand and choosing equipment carefully.

A practical hierarchy is:

1. Stop direct sunlight entering the room before it heats the interior.
2. Use natural ventilation when the outdoor air is cooler.
3. Use a fan for personal comfort when this is sufficient.
4. Cool only occupied rooms.
5. Choose an efficient, correctly sized inverter system.
6. Keep windows and doors closed while AC is operating.
7. Select a moderate thermostat setting.
8. Clean filters and maintain airflow.
9. Ensure exhaust hoses are properly sealed on portable units.
10. Arrange qualified servicing and responsible refrigerant recovery.

An oversized system is not necessarily better. It may switch on and off frequently, provide poor humidity control and operate less efficiently. An undersized system may run continuously without reaching the desired temperature.

Correct sizing is therefore both a comfort and carbon issue.

Businesses should treat cooling as a managed source of emissions rather than an unavoidable fixed cost.

The most useful actions include:

• sub-metering cooling electricity separately
• reviewing operating hours against actual occupancy
• zoning the building so empty spaces are not cooled
• setting cooling at 24°C or above where appropriate
• preventing heating and cooling from operating simultaneously
• maintaining a suitable gap between heating and cooling set points
• cleaning filters, coils and ventilation components
• investigating sudden increases in electricity consumption
• recording refrigerant type, charge and top-ups
• repairing leaks promptly
• replacing high-GWP refrigerants where technically appropriate
• reducing heat from lighting and equipment
• and using building-management systems to optimise performance

In England and Wales, air-conditioning systems with a combined effective rated output above 12 kW must be inspected by an accredited energy assessor at least once every five years. The inspection is intended to identify inefficient, oversized or poorly controlled systems and opportunities to reduce energy, carbon and operating costs.

Businesses should not treat the inspection as a paperwork exercise. Its recommendations can identify faults, inappropriate settings and maintenance problems that may otherwise remain hidden for years.

Air conditioning is not inherently sustainable, but neither is it inherently irresponsible.

Its environmental performance exists on a spectrum.

At one end is a poorly maintained portable unit cooling an unshaded room through an open window, powered by grid electricity and containing a high-impact refrigerant.

At the other is a correctly sized, high-efficiency system serving an occupied space only when needed, powered largely by low-carbon electricity, using a lower-impact refrigerant and operating in a building designed to keep heat out.

Both are called air conditioning. Their climate impacts can be dramatically different.

We should also recognise that cooling is sometimes essential. Hospitals, care homes, server rooms, food storage facilities and buildings occupied by medically vulnerable people cannot always rely on open windows and fans.

The aim should not be to deny necessary cooling. It should be to provide it as efficiently and responsibly as possible.

Air conditioning reveals one of the central challenges of climate adaptation.

As temperatures rise, people need protection from heat. Yet meeting that need through inefficient equipment, carbon-intensive electricity and leaking refrigerants can add to the problem driving those temperatures higher.

Britain is still near the beginning of this transition. Only a small minority of UK households currently use air conditioning, while commercial cooling is already widespread in offices, shops, healthcare and hospitality.

The choices made now will shape the future footprint of British cooling.

A portable air conditioner bought during a heatwave may provide immediate relief, but it should not become a substitute for better buildings. A renewable tariff can reduce reported operational emissions, but it cannot repair a leaking refrigerant circuit. A highly efficient system can still waste energy if it cools empty rooms or maintains unnecessarily low temperatures.

The most sustainable unit of cooling remains the heat that never enters the building.

Where active cooling is necessary, efficiency matters. Controls matter. Maintenance matters. Refrigerants matter. The source of electricity matters.

The real question is not simply whether air conditioning is "eco-friendly". It is whether we can keep homes, workplaces and public buildings safe and comfortable while using the least energy, causing the least environmental damage and remaining honest about the emissions that cannot yet be avoided.

That is the same discipline we bring to every business we work with at Carbon Neutral Britain: measure carefully, reduce first, be precise about what has actually been achieved, and use verified climate finance only for what genuinely remains. If you would like help measuring the footprint of your building's cooling, reducing what you can and understanding how responsible carbon offsetting fits into a credible climate strategy, you can become a Carbon Neutral Business or get in touch and we can start with your data.