How much do air conditioners add to energy bills?

That figure is a running cost, not a purchase price, and it sits on top of a bill that is already dominated by something else. More than half of a typical household energy bill goes on heating rooms and hot water². Cooling is a seasonal addition to that baseline, and it arrives in the months when the heating load is lowest.

What follows sets out the headline cost, why it varies so much between homes, how cooling and heating modes differ, how to work out a figure for a particular unit, and what the wider energy picture means for a household trying to keep control of its bills.

What an air conditioner adds to the bill

The honest answer is that it depends on the unit and the hours, and the only published UK figure for a typical case is the hourly one. National Energy Action puts a typical portable air conditioner of 1,000 to 1,500W at around 26 to 39p per hour, and notes that this is roughly 14 to 20 times more than a fan¹. That range is wide because it spans both the power rating of the unit and the electricity unit rate being paid.

The unit rate is the part households often overlook. Ofgem's explanation of how a bill is calculated sets out that the total depends on how much energy is used, the type of energy used, the type of meter installed, and how the bill is paid, for example by Direct Debit². Two identical air conditioners in two identical flats can therefore produce different hourly costs purely because of the tariff and payment method behind them.

For context on scale, a fridge and freezer account for 13% of an average household energy bill⁶. That is a continuous load running every hour of the year. An air conditioner is the opposite: a high-power load running for a small number of hours, concentrated into the warmest weeks. Its annual share of a bill is therefore driven almost entirely by how many hours it is switched on, not by its presence in the home.

Why running costs vary between homes

Independent guidance is consistent that actual costs vary depending on a home's insulation, temperature settings, energy prices and how the system is used⁷. Those four variables explain most of the spread between one household's experience and another's.

Insulation and airtightness matter because they set how quickly a cooled room warms back up. A well-insulated home holds a lower temperature for longer, so the compressor cycles less. A leaky home loses the cooled air and the unit runs closer to continuously. The same guidance notes that bigger houses are likely to cost more to run since there is much more space that needs heating, and the same logic applies to cooling a larger volume⁸.

The building's overall energy performance is the best available proxy for this. An EPC A or B rated home of 90m2 costs £1,574 a year to run, while EPC D rated homes, which are most existing homes, spent 27% more on their energy bill overall and 53% more on their gas bill than EPC A and B rated homes⁹. Those figures cover the whole bill rather than cooling alone, but they show how much the fabric of the home moves the numbers.

Cooling versus heating: which mode costs more

Air conditioning is often discussed as though it were a single mode, but a reversible unit in heating mode is doing a different job with a different efficiency. The regulatory figures that exist describe cooling. Approved Document L sets a minimum seasonal energy efficiency ratio of 4.0 for comfort cooling systems⁴, and the consultation version for Wales sets a minimum of 4.6 for new dwellings⁵. Those are cooling performance standards, and they are the only efficiency figures the guidance provides.

Heating mode is a separate measure, and the two should not be assumed to cost the same per hour of operation. What can be said is that the wider evidence on electric heating is cautionary. Official guidance notes that if a home is not well insulated, installing a heat pump may increase energy bills instead, because electricity is more expensive than gas¹⁰. An air conditioner in heating mode faces the same unit-rate disadvantage relative to a gas boiler.

There is also a question of how common cooling actually is. Official statistics for winter 2025 record that 5% of households said they used air conditioning³. That is a small base, and it means most UK homes have no cooling equipment at all, relying on windows, shading and fans instead.

How to estimate your own running cost

Two published formulas do the same job in slightly different units. Smart Energy GB gives it as appliance power rating in kW multiplied by electricity unit cost in pounds multiplied by time used in hours equals running cost¹¹. National Energy Action's Northern Ireland guidance gives the per-hour version: appliance running cost in pence per hour equals power rating in watts multiplied by electricity unit rate in pence per kWh, divided by 1,000¹².

Both need the same two inputs: the unit's power rating, which is on the label or in the manual, and the electricity unit rate, which is on the bill. Neither formula requires anything else, and neither accounts for cycling, so a unit that reaches its set temperature and idles will cost less in practice than the formula suggests.

For households that would rather not do the arithmetic, the Consumer Council provides an appliance cost checker that helps estimate the running costs of appliances, offering tips to save money and improve energy efficiency¹³. Its single appliance checker shows how much appliances cost to run on a per-minute, per-hour and per-day basis¹⁴.

Ways to limit the bill impact

The most direct lever is hours of use, because the hourly cost is the whole cost. Beyond that, the general measures that reduce a household's exposure to high electricity prices apply here as they do elsewhere.

Reducing the thermostat by 1°C could save up to 25% of heating bills and associated carbon, according to official guidance¹⁵. Independent guidance puts the same kind of adjustment at up to 10% on an annual fuel bill from reducing room temperatures by 1°C¹⁶. The two figures differ, and they are measuring different things, but both point the same way: a small change in set temperature has a disproportionate effect on consumption.

For homes with a combi boiler, lowering the flow temperature can save 6 to 8% on the heating bill¹⁷. That is a heating measure rather than a cooling one, but it illustrates the principle that the biggest savings usually come from the systems that run for the most hours, not the ones that run for a few weeks.

Air conditioning and the wider energy picture

Cooling sits inside a bill that is shaped by forces well beyond the household's control. The wholesale cost of energy is the biggest factor affecting energy bills¹⁹, and the price cap itself moves with it: Ofgem's August 2025 announcement described a change adding around £1.23 a month to the average household bill²⁰.

The direction of travel has been upward. Energy bills rose by 10% at the same time as the Winter Fuel Payment was cut²¹, and the average older household saw bills increase by up to 15% in real terms compared with winter 2023/24²². Against that background, an appliance that costs 26 to 39p an hour is a discretionary load, and one of the easier ones to switch off.

Time-of-use tariffs are sometimes presented as a way to cut the cost of high-draw appliances, and they can be, but the condition matters. Official guidance notes that where heating patterns are not well aligned to the tariff, time-of-use tariffs can increase fuel bills²³. Solar Energy UK explains the underlying pattern: the price of electricity varies throughout the day, tending to be cheap during the day and more expensive in the evening²⁴. Evening cooling runs against that pattern.

Demand side response, the practice of shifting consumption to when the grid is under less strain, could make household energy bills cheaper²⁵. For a household, the practical meaning is that when cooling runs matters as much as how much it runs.