26.32p per kWh Ofgem price cap, October to December 2026
Air Conditioning Running Costs, Hour by Hour
Air conditioning running costs for a modern 2.5kW or 3.5kW split unit come to about 7p to 9p an hour on a typical day at the current price cap. We fit units across London and the South East, and this guide shows the sums behind every figure.
- Figures at the October 2026 price cap
- Cooling and heating costs
- Free calculator on this page
Last updated: October 2026
The short answer
How much does air conditioning cost to run per hour?
A modern 3.5kW split unit costs about 9p an hour to cool a living room on a typical UK summer day. That is 0.35kW of electricity at the Ofgem cap of 26.32p per kWh. Aircova works out these figures for every room we survey, so you know the cost before we fit.
Here is the worked example in full. A 3.5kW unit is rated to move 3.5kW of heat out of a room. On a warm day it runs at about half that output, and a good inverter unit moves about 5kW of heat for every 1kW of electricity at that load.
- Average output. 3.5kW rating at about 50% load gives 1.75kW of cooling.
- Electricity used. 1.75kW divided by an efficiency of 5 is 0.35kW of power.
- Cost per hour. 0.35kWh at 26.32p comes to 9.2p for each hour of running.
- Cost per day. Eight hours of use comes to 2.8kWh, or about 74p.
- Cost per month. Thirty days at eight hours a day comes to about £22.
The 26.32p figure is the average direct debit unit rate under the Ofgem price cap from 1 October to 31 December 2026. Ofgem also notes there is no VAT on electricity from 1 October 2026 to 31 March 2027, so the cap rate is what you pay per kWh.
Your own rate depends on your region, payment method and tariff. Fixed and time of use tariffs can sit well above or below the cap, so check the unit rate on your latest bill.
| Unit and mode | Mild day | Typical day | Heatwave or cold snap |
|---|---|---|---|
| 2.5kW cooling | 3p | 7p | 15p |
| 3.5kW cooling | 5p | 9p | 21p |
| 2.5kW heating | 4p | 8p | 18p |
| 3.5kW heating | 6p | 12p | 25p |
These air conditioning running costs are our estimates for a modern inverter split unit. Mild day: 30% load. Typical day: 50% load. Heatwave or cold snap: 80% load with lower efficiency. The standing charge is paid anyway, so it is not included.
Bedroom, 2.5kW, eight hours a night
A typical summer night uses about 2kWh, which costs around 53p. Thirty nights comes to about £16. In a heatwave the same unit may use 4.6kWh, or about £1.20 a night.
Living room, 3.5kW, eight hours a day
A typical warm day costs about 74p, or £22 for a month of daily use. During a run of 30°C days, expect closer to £1.68 a day while the heat lasts.
Living room heated in winter, 3.5kW
Eight hours of heating on a typical winter day uses about 3.5kWh, or 92p. In a cold snap that rises to about £1.97 a day, as the unit works harder.
Free tool
Running-cost calculator for your unit
Use this tool to estimate air conditioning running costs for your own room. Pick the unit size, the mode and how hard it will work. The unit rate is set to the October 2026 price cap, and you can change it to match your bill.
Estimated cost per day
£0.74
Per hour 9.2p, using about 2.8kWh a day
For 30 days: £22.11
About £22.11 for a 30 day month at this pattern.
Based on a 3.5kW unit cooling on a typical day, drawing about 0.35kW on average.
Send my result on WhatsAppThis is an estimate. Real use depends on the room, the weather and the model.
The tool divides the unit size, times the load, by a set efficiency for each condition. Cooling uses 6, 5 and 3.5. Heating uses 4.5, 4 and 3, as efficiency drops when the outdoor air gets colder.
Not sure which size you need? Our BTU calculator gives a starting size for each room, and a correctly sized unit is the cheapest one to run.
Reading the label
kW input vs output, SEER and SCOP explained
The kW size on a split unit is its output, not what it takes from the mains. A 3.5kW unit moves up to about 3.5kW of heat. It does that by pumping refrigerant, which needs far less power than making heat or cold directly.
The power the unit draws is listed on the spec sheet as power input. On a modern 3.5kW wall unit at full rated output, it is often around 0.8 to 1kW. Most of the time the unit runs well below full output, so the average draw is lower still.
What SEER means
SEER is the seasonal energy efficiency ratio for cooling. It divides the cooling delivered across a typical season by the electricity used. A SEER of 6.5 means 6.5kWh of cooling for each 1kWh you pay for.
On the energy label, A++ for cooling needs a SEER of at least 6.1, and A+++ needs at least 8.5. Many units we fit are A++ for cooling or better.
What SCOP means
SCOP is the same idea for heating. Modern inverter units give about 3 to 4kW of heat per kW of electricity, which is a SCOP of around 4. An electric heater gives 1kW of heat per kW, so it costs about four times as much to run.
Why two units of the same size cost different amounts
Two 3.5kW units can have very different SEER and SCOP figures. A unit with SEER 8 uses nearly 20% less power for cooling than one with SEER 6.5. Over years of use, that gap can be worth more than a lower purchase price.
How modern units save power
How inverter units keep the cost down
An inverter unit changes the speed of its compressor to match the room. It runs hard to reach your set temperature, then slows right down to hold it. Older fixed speed units switched fully on and off instead.
Starting and stopping a compressor wastes power, and the room swings warm and cool. A slow, steady inverter compressor works at its most efficient point for most of the day.
This is why we suggest leaving a unit to hold a steady temperature rather than turning it off and on many times. The first hour after switching on usually costs the most.
The wall-mounted air conditioning units we fit are inverter models running on R32. Our quietest units guide covers the same slow running from the noise side.
Winter use
Air-to-air heat pump running costs in winter
A split unit in heating mode is an air-to-air heat pump. The outdoor unit collects warmth from outside air, even below freezing, and the indoor unit blows it into the room.
Air-to-air heat pump running costs depend on how cold it is outside. On a mild day the unit may give 4 to 4.5kW of heat per kW of power. On a frosty day that can fall to around 3, and the unit also pauses to defrost.
Heating vs storage heaters and panel heaters
Storage heaters, panel heaters and oil radiators all turn 1kWh of electricity into 1kWh of heat. A heat pump with a SCOP of 4 turns the same 1kWh into about 4kWh of heat.
Storage heaters charge on cheaper night rates, which vary by supplier and region. If your night rate is above about 6.6p per kWh, a heat pump at SCOP 4 heats for less, before counting the heat storage heaters lose during the day.
Many London flats with no gas supply run on storage heaters. Swapping them for a heat pump may also qualify for the £2,500 heat pump grant, which we check at the survey.
Compared with gas
At the cap, gas is 7.97p per kWh. A boiler at 90% efficiency gives heat for about 8.9p per kWh. A heat pump at SCOP 4 gives heat for about 6.6p per kWh, so the gap is smaller than with electric heaters.
The Energy Saving Trust air-to-air guide notes there is still little UK data on how these systems perform in homes. Treat our figures as estimates, not a promise.
| Heat source | Heat per kWh in | Cost per kWh of heat | 14kWh of heat |
|---|---|---|---|
| Electric panel heater or oil radiator | 1kWh | 26.3p | £3.68 |
| Gas boiler at 90% | 0.9kWh | 8.9p | £1.24 |
| Heat pump on a frosty day, COP 3 | 3kWh | 8.8p | £1.23 |
| Heat pump, SCOP 4 | 4kWh | 6.6p | £0.92 |
Electricity at 26.32p and gas at 7.97p per kWh, Ofgem cap averages for October to December 2026. Standing charges are left out, as you pay them whichever heating you use.
Side by side
Portable units, fans and heaters compared
The cost to run air conditioning depends a lot on the type. A fitted split keeps the hot condenser outside, while a portable unit keeps it in the room with you.
| Option | Typical power draw | Cost per hour | What you get |
|---|---|---|---|
| Desk or pedestal fan | About 40W | About 1p | Moving air, no drop in room temperature |
| Portable air conditioner | Often around 1kW | Up to about 26p | Some cooling, hot hose and noise in the room |
| 2.5kW split, typical day | About 0.25kW | About 7p | Steady cooling, condenser outside |
| 3.5kW split, heatwave | About 0.8kW | About 21p | Full output on the hottest days |
Why portable units cost more
A portable unit runs its compressor and condenser inside the room. The exhaust hose gets hot, and warm air leaks back in around the window kit. So it draws more power for less cooling.
Our portable vs split air conditioning guide compares the two in full, including noise and upfront price.
Electric heaters in winter
- 2kW of heat
- About 53p an hour
- No cooling in summer
- Up to about 4kW of heat
- About 12p an hour, typical
- Cools in summer too
Practical tips
How to cut your air conditioning running costs
Most savings come from asking the unit to do less work. Each tip below cuts the load, raises the efficiency, or moves your use to a cheaper rate.
- Set cooling to about 24°C, not 18°C. Each degree lower adds load.
- Close blinds on south and west windows before the sun hits them.
- Keep doors and windows shut while the unit runs.
- Use the timer to start cooling 30 minutes before bed, not all afternoon.
- Hold a steady temperature instead of switching on and off many times.
- Use night or quiet mode in bedrooms, as it runs the fan slower.
- Rinse the indoor unit filters every few weeks in heavy use.
- Keep plants, bins and covers at least 30cm clear of the outdoor unit.
- Run the unit in cheaper hours if you are on a time of use tariff.
- Compare SEER and SCOP before you buy, not just the price.
Servicing and efficiency
Dirty filters and coils make the compressor work harder for the same cooling. A yearly air conditioning service cleans the coils, checks the condensate drain and confirms the unit is working as designed.
Size matters as much as rating
An undersized unit runs at full output for hours on hot days, where efficiency is lowest. A unit that is far too big costs more to buy and cycles too often. Correct sizing keeps the unit near its best part load.
Thinking about the purchase price too? Running costs are only part of the sum. Our air conditioning cost page shows fitted prices, from £2,195 with VAT for a 2.5kW wall-mounted unit. For heating, see our air-to-air heat pump prices.
At the handover after an air conditioning installation, we show you the timer and night mode, so the unit runs at its cheapest from day one. For a firm figure for your home, get an instant quote online, or ask about multi-split air conditioning if you want several rooms on one outdoor unit.
FAQs
Running cost questions
How much does it cost to run air conditioning for 8 hours?
About 53p for a 2.5kW unit and 74p for a 3.5kW unit on a typical summer day. Those figures use the October 2026 cap rate of 26.32p per kWh and a modern inverter split. In a heatwave the same units can cost around £1.20 and £1.68 for 8 hours. A portable unit drawing about 1kW could cost up to £2.11 for the same time.
Is it cheaper to leave air conditioning on all day?
Often yes, in the hottest weeks. An inverter unit uses the most power when it pulls a hot room down, then little to hold it. Switching off when you go out for an hour can cost more than leaving it at a steady 24°C. For a full day out, use the timer to start it 30 minutes before you get home instead.
Does air conditioning use a lot of electricity?
Not compared with most heating appliances. A 3.5kW split unit on a typical day draws about 0.35kW on average. A 2kW fan heater draws more than five times as much. The cost to run air conditioning only climbs high in a long heatwave, or with a portable unit.
Is an air-to-air heat pump cheaper to run than storage heaters?
Usually yes. Storage heaters give 1kWh of heat per kWh, while a heat pump with a SCOP of 4 gives about 4kWh. At SCOP 4 the heat pump beats any night rate above about 6.6p per kWh. Storage heaters also lose heat during the day when you may not need it, while a heat pump heats only when the room calls for it.
Does heating mode cost more than cooling?
Slightly more per hour in most UK homes. Winter brings a bigger gap between indoor and outdoor temperature than summer, so the unit works harder. Efficiency also falls on frosty days, and the unit pauses to defrost. A 3.5kW unit costs about 9p an hour cooling and about 12p heating on a typical day.
What temperature should I set to keep running costs low?
Set cooling to about 24°C and heating to about 20°C. A room at 24°C feels cool when it is 30°C outside, because the unit also removes moisture. Every degree further from the outdoor temperature adds work for the compressor. Fan speed on auto lets the unit pick the most efficient setting.
How much electricity does a 3.5kW air conditioner use?
At full output a modern 3.5kW split unit often draws around 0.8 to 1kW, which you will find as power input on the spec sheet. On a typical day it runs nearer half output and draws about 0.35kW. The 3.5kW figure is the cooling it delivers, not the power it takes from the mains.
Will running costs change when the price cap changes?
Yes. Ofgem sets the cap every three months, so the unit rate and every cost on this page move with it. The current figure of 26.32p per kWh applies from 1 October to 31 December 2026. Type your own rate into the calculator above to see the effect of any change or tariff.
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