Is air conditioning expensive to run? UK running costs explained

No, air conditioning is not as expensive to run as most people fear. A typical home unit costs roughly 20p to 65p per hour to run for cooling at current electricity prices, which works out at tens of pounds a month for sensible use, not hundreds. A small bedroom unit run overnight might add around £28 a month to your bill; heavy whole-home cooling during a heatwave is more like £75 a month.

Here is the maths behind that, at the current price cap rate, with everything shown so you can redo it for your own unit and tariff. The headline number to remember: a unit's electrical power in kW, multiplied by 26.11p, gives you the cost per hour.

If you would rather not do the sums by hand, our free running cost calculator does the same maths for your unit, hours and tariff, with the working shown.

Running costs use the Ofgem price cap rate of 26.11p per kWh for electricity, for 1 July to 30 September 2026. The cap changes every three months (the next rate is announced around 26 August 2026), so check your own latest bill before budgeting.

How to work out your air conditioning running cost

The formula is simple:

electrical power (kW) x electricity price (p/kWh) = pence per hour

So a unit drawing 1 kW of electricity, at the current 26.11p per kWh, costs 1 x 26.11 = about 26p an hour. Run it for 5 hours and that is 5 kWh, or about £1.31 for the day.

There is one trap that makes most online estimates wrong, so it is worth getting straight. Spec sheets headline the cooling or heating output in kW (for example "2.5kW"). That is not what you pay for. You pay for the electrical input, which is much lower because the unit moves several units of heat for every unit of electricity it uses. Always build your sums on the input power (or on measured kWh from a plug meter or your smart meter), never on the nameplate output, or you will badly overstate the bill.

As a rule of thumb, a typical home air conditioner draws somewhere between 0.5 and 2.5 kWh per hour depending on its size, its efficiency, the room, and how cold you set it.

How much does air conditioning cost per hour by unit size?

This table uses the formula above (input kW x 26.11p) across the range of input power for common home systems.

For context, portable units typically draw 0.75 to 1.5 kW, single splits 0.8 to 2.5 kW, and multi-split or ducted systems 1 to 5 kW. Most households running a single room sit comfortably in the 20p to 65p per hour band.

How much does it cost per day, and per month?

For 8 hours: a unit drawing 0.6 kWh per hour over 8 hours uses 4.8 kWh, which is about £1.25. A thirstier unit at 1.0 kWh per hour uses 8 kWh, or about £2.09 for the same 8 hours.

For a month, here are three realistic summer scenarios. Treat these as illustrative estimates, not promises: real use varies with the weather, your insulation, and the temperature you set.

Across a typical UK summer, most homes cooling one or two rooms sensibly are looking at tens of pounds a month, not the eye-watering bills the question implies. If overnight cooling is your main aim, our guide to bedroom air conditioning covers choosing a quiet, efficient unit for that light bedroom scenario.

Does air conditioning use gas?

No. Home air conditioning runs entirely on electricity. It does not burn gas, petrol or any other fuel.

The only "gas" involved is the refrigerant, a sealed fluid (commonly R32 in modern UK domestic units) that circulates inside the system to move heat around. It is not consumed or burned, and it should never need topping up unless there is a leak. So when people ask "does air con use gas", the honest answer is: it uses electricity to run, and a sealed refrigerant that does not run out in normal use.

What do SEER, SCOP and COP mean?

Efficiency is the single biggest factor in what your unit costs to run, so it is worth understanding the labels.

• SEER (Seasonal Energy Efficiency Ratio) measures seasonal cooling efficiency.

• SCOP (Seasonal Coefficient of Performance) measures seasonal heating efficiency.

• EER and COP are the same idea measured at a single test point rather than across a season.

In every case, higher is better: it means more cooling or heating per unit of electricity. Modern UK domestic splits commonly carry a SEER of around 6.5 to 8.5 and a SCOP of around 4.0 to 4.6, with A++ or A+++ energy labels. As a buying tip, look for a SEER of 7 or above.

Inverter technology is the other big lever. An inverter unit modulates its output up and down instead of switching on and off at full blast, and that can cut power consumption by up to 40% compared with older fixed-speed compressors. Almost every quality split sold today is an inverter unit.

Is using air conditioning for heating cheaper than gas?

This is the part most cost guides miss, and it is genuinely useful. A reverse-cycle air conditioner (an air-to-air heat pump, which heats as well as cools) can deliver heat more cheaply than a gas boiler for a single room at current prices.

It sounds wrong, because electricity costs about 3.5 times as much as gas per unit (26.11p versus 7.33p per kWh on the current cap). But a heat pump does not turn one unit of electricity into one unit of heat. With a SCOP of around 4, it delivers roughly four units of heat for every unit of electricity. That efficiency more than cancels out the price gap.

Here is the cost to deliver 1 kWh of useful heat:

At current rates, a reverse-cycle unit with a SCOP around 4 heats a room at roughly 6.5p per kWh, against roughly 8.1p from a gas boiler, and it is around four times cheaper than any plug-in electric heater. The margin narrows as it gets colder and real-world SCOP drops, so treat this as "often cheaper, depending on the unit and the weather" rather than a blanket guarantee. For whole-home heating the picture is more nuanced, but for taking the chill off a single room, reverse-cycle AC is one of the cheapest sources of heat you can buy.

One thing to be clear about: reverse-cycle AC is an air-to-air heat pump, which is a different product from the air-to-water heat pumps that feed your radiators. If you want to understand the grants angle, see the running-cost reducers below.

Are portable units more expensive to run than splits?

Yes. Portable units are less efficient than fixed splits, mainly because warm air leaks back into the room through the exhaust hose and the single-box design is a compromise. For the same cooling effect, a portable typically costs more per hour to run than a fixed split, and it cools less effectively too. If a portable still suits your situation, our roundup of the best portable air conditioners highlights the more efficient models. If you want to compare the two properly, see our portable vs split air conditioners guide. For a permanent fix in a room you use a lot, a wall-mounted split system is almost always the better long-term call on both comfort and running cost.

How can I cut my air conditioning running costs?

The biggest savings come from how you use the unit and how you set it up.

• Set a sensible temperature. Cooling to 18°C costs far more than cooling to 24°C. Each degree lower means longer run times and more electricity. Aim for the warmest setting that still feels comfortable, usually 22°C to 24°C.

• Keep the heat out in the first place. Close blinds and curtains on sunny windows, and keep doors shut so you are only cooling the room you are in. The less heat that gets in, the less your unit has to work.

• Use timers and smart controls. Cool the room before you need it and let it coast, rather than running flat out all day. Inverter units are efficient at maintaining a set temperature, so leaving one ticking over can beat repeatedly blasting a hot room from cold.

• Clean the filters. A clogged filter makes the unit work harder for less effect. A quick clean every few weeks in summer keeps it efficient.

• Right-size the unit. An undersized unit runs flat out and never quite copes; an oversized one short-cycles. The correct kW for your room size keeps running costs down.

• Choose efficiency when you buy. A higher SEER and an inverter compressor pay for themselves over the life of the unit. To budget the upfront side, see how much air conditioning costs to install.

On grants: because a reverse-cycle unit is a heat pump, you may have heard about funding. A £2,500 air-to-air heat pump grant became available in England and Wales on 28 April 2026, but the conditions are strict. It applies only to reverse-cycle units that replace an existing fossil-fuel or electric heating system, installed by an MCS-certified installer. It does not cover comfort-cooling AC fitted alongside a retained gas boiler, and it does not cover portable units. It is also separate from the larger £7,500 grant, which is for air-to-water heat pumps. Air conditioning is not "free", so check the current rules before you assume you qualify.

Running costs at a glance

Figures correct as of August 2026, based on the Ofgem price cap rate of 26.11p per kWh (1 July to 30 September 2026). The cap changes quarterly, with the next rate announced around 26 August 2026, so check current rates and your own bill before budgeting.