The cost of heating a room with air conditioning depends on the system efficiency, heat required by the room and your electricity tariff. Modern air conditioning operates as an air to air heat pump, so it can deliver several units of heat for each unit of electricity consumed. At the current Ofgem average electricity rate of 26.11 pence per kWh, a system using 0.5 kW of electricity would cost approximately 13 pence per hour while operating at that level. In practice, inverter systems continually vary their electricity consumption as heating demand changes.
At a Glance
If you are short on time, here is what you need to know.
Is air conditioning expensive to use for heating? Not necessarily. Because it operates as a heat pump, it can provide several units of heat for each unit of electricity consumed.
What is the current electricity price? The Ofgem average electricity unit rate from 1 July to 30 September 2026 is 26.11 pence per kWh for a standard variable tariff paid by Direct Debit.
Does a 3.5 kW air conditioner use 3.5 kW of electricity? No. The 3.5 kW figure normally describes heating or cooling capacity, not electrical consumption.
What does COP mean? It compares the heat delivered with the electricity consumed.
What does SCOP mean? It measures heat pump efficiency across a representative heating season.
Does the system use the same amount of electricity all day? No. Modern inverter systems vary their output according to heating demand.
Reading time: 11 to 13 minutes
Last reviewed: August 2026
Air Conditioning Is a Heat Pump When It Is Heating
Before looking at running costs, it is important to understand what the equipment actually does.
Modern residential air conditioning is normally a reversible air to air heat pump.
During summer, heat is transferred from inside your home to outside.
During winter, the refrigeration cycle reverses.
The outdoor unit collects heat from the outside air and transfers it into the room.
The UK Government Energy Technology List describes air to air heat pumps as electrically operated refrigeration systems that transfer heat from outside a building to the air inside it.
That is fundamentally different from direct electric heating.
The system is using electricity to move heat rather than creating every unit of heat directly from an electrical heating element.
What Does COP Mean?
COP means Coefficient of Performance.
Energy Saving Trust gives a simple explanation.
If a heat pump has a COP of 3, it delivers three units of heat for every unit of electricity it consumes.
For example:
If a room needs 3 kW of heat and the heat pump is operating at a COP of 3, the theoretical electrical demand would be around:
1 kW
If the same heat pump was operating at a COP of 4, producing the same 3 kW of heat would theoretically require around:
0.75 kW
This is why heating capacity and electrical consumption should never be confused.
A 3.5 kW Air Conditioner Does Not Use 3.5 kW of Electricity
This is probably the most common misunderstanding we hear.
A homeowner sees:
3.5 kW air conditioning system
and assumes:
“The system uses 3.5 kW of electricity.”
It normally does not.
The 3.5 kW figure usually refers to the amount of heating or cooling the system can deliver under specified conditions.
The electricity required to produce that output can be considerably lower because the system is transferring heat.
That distinction is fundamental when calculating running costs.
What Is the Current UK Electricity Price?
Ofgem sets an energy price cap for households on standard variable tariffs.
From 1 July to 30 September 2026, the average electricity unit rate for a household paying by Direct Debit is:
26.11 pence per kWh
Actual rates vary by region, tariff and payment method. Customers on fixed tariffs may pay something different.
Ofgem has already announced that the average electricity unit rate from 1 October to 31 December 2026 will be 26.32 pence per kWh under the relevant price cap arrangements.
Because tariffs change, any article promising a permanent fixed running cost will quickly become inaccurate.
The best approach is to understand the calculation.
How Do You Calculate Air Conditioning Heating Cost?
The basic calculation is simple.
Take the electrical power being consumed.
Multiply it by your electricity unit rate.
For example, imagine the air conditioning is currently consuming:
0.5 kW
At 26.11 pence per kWh:
0.5 multiplied by 26.11 pence gives approximately:
13.1 pence per hour
If the system was consuming:
0.75 kW
the cost would be approximately:
19.6 pence per hour
At:
1 kW
the cost would be:
26.11 pence per hour
But this is where hourly running cost calculations start to become misleading.
The system will not necessarily consume 0.5 kW, 0.75 kW or 1 kW continuously.
Modern Air Conditioning Changes Its Power Consumption
Residential split systems use inverter technology.
That means they can adjust their output.
Imagine you enter a cold garden office first thing in the morning.
The room temperature is 13°C.
You select 20°C.
The system initially has a significant heating requirement.
It works harder.
As the room approaches 20°C, the amount of heat required falls.
The system can reduce its output and concentrate on maintaining the temperature.
So:
Eight hours switched on does not mean eight hours at maximum electrical consumption.
This is why actual energy consumption is more useful than simply asking how much the system costs for every hour the remote control is switched on.
ClimateWorks Insight
The phrase “cost per hour” sounds helpful because everybody understands it.
For inverter air conditioning, it can also be misleading.
The system does not behave like a fixed 2 kW electric heater that simply draws its rated power whenever the heating element is fully energised.
Its consumption rises and falls with demand.
A better question is:
How much electricity will this room need over a typical day or heating season?
That depends as much on the room as the air conditioner.
What Is SCOP?
COP describes efficiency at a particular operating condition.
SCOP means Seasonal Coefficient of Performance.
The Government Energy Technology List defines SCOP as the heating required over a representative heating season divided by the electricity consumed to provide it.
Energy Saving Trust explains why this matters.
Heat pumps do not operate at the same efficiency throughout the year.
When outdoor temperatures fall, they generally need to work harder.
SCOP therefore gives a more useful indication of overall seasonal performance than looking at one COP figure measured under one set of test conditions.
A Simple SCOP Example
Imagine a heat pump has a seasonal efficiency equivalent to a SCOP of 4.
Over the relevant standardised seasonal calculation, every:
1 kWh of electricity
corresponds to approximately:
4 kWh of heat delivered
At an electricity rate of 26.11 pence per kWh, purchasing that one unit of electricity costs approximately:
26 pence
This is the reason air to air heating can be particularly attractive where the alternative is direct electric heating.
It is using electricity much more effectively.
Real household performance will vary from the published SCOP because your property will not exactly reproduce laboratory test conditions.
What Makes Heating Cost Increase?
Several factors can make the system work harder.
Cold Outdoor Temperatures
As outside temperatures fall, the heat pump has to work harder to transfer heat indoors.
Energy Saving Trust notes that heat pump efficiency varies with outside temperature, which is one reason seasonal efficiency is more informative than a single COP figure.
Poor Insulation
If heat leaves the room quickly, the air conditioning needs to replace it.
Insulation affects running cost regardless of which heating technology you use.
Large Areas of Glass
Windows and glazed doors can increase winter heat loss.
Garden rooms and conservatories therefore require particular attention.
Very High Thermostat Settings
There is a big difference between maintaining a room at a comfortable temperature and asking the equipment to create tropical conditions in January.
Higher indoor temperatures normally increase heat loss and therefore energy demand.
Open Doors and Windows
Heating a room while continuously allowing cold outdoor air inside creates unnecessary demand.
Incorrect System Sizing
The equipment should be selected around the actual heating and cooling requirements of the room.
What Can Make Heating Cost Lower?
The opposite measures help.
- Good insulation
- Sensible temperature settings
- Closing external doors and windows
- Correct system sizing
- Efficient modern equipment
- Heating only rooms that actually need it
- Using schedules intelligently
- Making use of solar generation where available
The equipment is only one part of the energy calculation.
How the room is used matters enormously.
A Home Office Example
Imagine one person works from home five days a week.
The office is occupied from 8.30am until 5pm.
The rest of the property is largely empty.
One option is to heat the entire home.
Another is to provide independent heating to the office.
A dedicated air to air system allows the homeowner to control that room without automatically changing the temperature throughout the house.
Whether that saves money compared with the existing central heating depends on fuel prices, heating system efficiency and how the property is zoned.
But targeted room heating is one of the strongest practical benefits of air conditioning.
A Garden Room Example
Garden rooms make the comparison even clearer.
Many do not have central heating.
The usual alternatives are electrical.
A garden office may currently depend on an electric panel heater for eight hours every working day.
Installing air conditioning introduces heat pump technology instead.
During winter it provides efficient heating.
During summer it reverses and provides cooling.
The investment therefore solves two different problems with the same equipment.
A Typical Hampshire Example
A common ClimateWorks enquiry involves a home office in Hampshire that has become a permanent workplace.
The homeowner wants to know:
“How much will it cost me to heat all day?”
The correct answer is not to invent one pence per hour figure.
We need to consider:
- Room size
- Insulation
- Glazing
- Outdoor conditions
- Equipment selected
- Desired indoor temperature
- Electricity tariff
- How long the room is occupied
Only then can the homeowner form a sensible expectation of energy consumption.
A Typical Berkshire Example
Consider a loft bedroom in Berkshire.
The homeowner originally wants air conditioning because the room overheats during summer.
During winter, they discover that using heating mode for the bedroom can avoid needing additional direct electric heating.
The system may initially work harder to bring the room up to temperature.
Once comfortable, the inverter reduces output.
This illustrates why measuring energy over an evening provides much more useful information than assuming the equipment consumes its maximum input for the entire time it is switched on.
Is Air Conditioning Cheaper Than Electric Heating?
It can be significantly more efficient.
We cover this question in detail in our separate guide on air conditioning versus electric heating.
The fundamental reason is straightforward.
Direct electric resistance heating creates heat from electricity.
An air to air heat pump uses electricity to transfer additional heat from outside.
Government and Energy Saving Trust guidance recognise this efficiency advantage and use COP and SCOP to describe heat pump performance.
The actual monetary saving depends on the systems being compared and how they are used.
What About Gas Central Heating?
This is more complicated.
Electricity currently costs considerably more per purchased kWh than gas.
However, a heat pump can deliver several units of heat from each unit of electricity consumed.
A boiler and an air to air heat pump also heat a home differently.
One may heat the whole property through radiators.
The other may heat one individual room.
That means a simple comparison of electricity and gas unit rates does not tell you which option will be cheapest for a particular household.
The Department for Energy Security and Net Zero's 2026 research specifically modelled the energy use and running costs of reversible air to air heat pumps across different UK home types and scenarios, highlighting how much the answer depends on the building and heating strategy.
Can Solar Panels Reduce Heating Costs?
Potentially.
Air conditioning uses electricity.
Solar panels can supply some of that electricity while they are generating.
The challenge is that the greatest heating demand usually occurs during winter, when solar generation is lower.
Battery storage and time of use electricity tariffs can also influence the calculation.
We cover solar and battery storage separately because they deserve their own detailed guidance.
The important point is that air to air heating can form part of a wider electrically powered home energy strategy.
How Can I Measure My Actual Air Conditioning Running Cost?
This is increasingly useful.
Some modern systems and home energy monitoring platforms can provide information about electricity use.
Smart meters can also help homeowners understand their overall electricity consumption.
The Government Energy Technology List specifically recognises smart heat pump features capable of recording parameters including electricity consumption, heat delivered and operating time.
Real measured consumption from your own home is always more valuable than somebody else's estimate.
Your building is different.
Your thermostat settings are different.
Your weather is different.
Your usage is different.
Common Mistakes Homeowners Make
Assuming Heating Capacity Equals Electricity Consumption
A 3.5 kW heating output does not mean the equipment continuously consumes 3.5 kW of electricity.
Asking for One Guaranteed Cost Per Hour
An inverter system constantly changes its power consumption.
Ignoring the Electricity Tariff
Running costs change when unit prices change.
Using Maximum Electrical Input for Every Hour
Maximum demand does not represent normal operation throughout an entire heating period.
Ignoring the Room
Poor insulation and excessive heat loss can make any heating system work harder.
Setting an Unnecessarily High Temperature
The warmer you maintain a room relative to outside, the more heat the building loses.
Dr Julian Carter's Expert Commentary
“Homeowners naturally want a simple answer such as ten or twenty pence an hour, but that is not how modern inverter air conditioning works. Electricity consumption changes constantly as the room warms up and the heating demand falls. The useful figure is the energy consumed over time. A correctly sized air to air heat pump in a well insulated room can provide a very efficient form of targeted heating, particularly where the alternative is direct electric heating.”
Dr Julian Carter
Technical & Compliance Director
ClimateWorks
How the ClimateWorks Process Works
Step 1. Get Your Online Guide Price
Use the ClimateWorks online quotation tool.
Tell us which rooms you want to heat and cool and receive an initial guide price.
Step 2. Request a Site Survey
If the guide price fits your expectations, request a site survey.
Where winter heating is important, tell us.
We can then consider:
- Room dimensions
- Insulation
- Glazing
- Heating requirement
- Cooling requirement
- Equipment efficiency
- Indoor unit position
- Outdoor unit location
- Pipework
- Electrical requirements
- How frequently the room will be occupied
Step 3. Receive Your Final Price
Following the survey, we provide the final quotation based on the agreed installation.
You can then accept or decline.
Why Homeowners Choose ClimateWorks
We would rather explain why running costs vary than promise a figure that may have little relationship to your home.
Residential heating and cooling should be designed around how the property is actually used.
For one homeowner, air conditioning may primarily solve summer bedroom overheating.
For another, winter heating in a garden office may be equally important.
ClimateWorks works across Hampshire, Berkshire and Surrey to select systems around both requirements, giving homeowners a solution designed for year round use rather than one season.
Frequently Asked Questions
How much does air conditioning cost per hour for heating?
There is no fixed amount. If a system was consuming 0.5 kW of electricity at the current Ofgem average rate of 26.11 pence per kWh, that would equal approximately 13 pence per hour at that moment. Actual consumption continuously changes with heating demand.
Does a 3.5 kW air conditioner use 3.5 kW of electricity?
No. The stated capacity normally refers to heat output or cooling output rather than electrical consumption.
What is COP?
Coefficient of Performance compares the heat delivered with the electricity consumed. A COP of 3 means three units of heat are delivered for each unit of electricity used.
What is SCOP?
Seasonal Coefficient of Performance represents heat pump efficiency across a standardised heating season.
Does air conditioning use less electricity once the room is warm?
Modern inverter systems can reduce their output as the room approaches the selected temperature, so electricity consumption can fall substantially compared with the initial warm up period.
Does colder weather increase running costs?
Generally, yes. Heat pump efficiency varies with outdoor temperature and the building also tends to lose heat more quickly when it is colder outside.
Is air conditioning expensive to heat a garden room?
It depends on insulation, size and usage, but air to air heating can be particularly attractive where the alternative is regular direct electric heating.
Can I heat only one room?
Yes. Independent room control is one of the major advantages of split air conditioning.
Can solar panels help with heating costs?
Potentially. Solar generation can contribute towards the electrical demand of an air to air heat pump when electricity is being generated.
How can I get the most accurate running cost?
Use the actual electricity consumption of your system and multiply it by your own electricity unit rate. Monitoring consumption over several days or weeks provides a much better picture than a generic hourly estimate.
References
Ofgem
The average electricity unit rate under the energy price cap for a standard variable tariff paid by Direct Debit from 1 July to 30 September 2026 is 26.11 pence per kWh.
Energy Saving Trust
Energy Saving Trust explains COP and seasonal efficiency and why real heat pump running costs vary according to outdoor temperatures, system design and household conditions.
UK Energy Technology List
Government technical guidance defines air to air heat pumps and SCOP and explains how seasonal heating efficiency is assessed.
Department for Energy Security and Net Zero
Research published on 9 July 2026 models reversible air to air heat pump energy use, running costs and suitability across different UK home types and heating scenarios.
Author Bio
Dr Julian Carter is Technical & Compliance Director at ClimateWorks and specialises in residential air conditioning, air to air heat pumps, system efficiency and indoor comfort. Drawing on practical experience from installations across Hampshire, Berkshire and Surrey, Dr Carter provides evidence based guidance to help homeowners understand the real world costs and benefits of using modern air conditioning for year round heating and cooling.
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