What Air Conditioning Actually Costs to Run in the UK

Why there's no single figure for running costs

One of the most common questions we're asked is simply how much air conditioning costs to run. There's no single honest answer, because it depends on the size of the unit, how well the property retains heat or cool, how the system is used day to day, and current electricity prices, which have moved around considerably in recent years.

Rather than quoting a figure that won't apply to your home or business, it's more useful to understand the factors that actually drive cost, because these are the things you can influence.

Unit size and how hard it has to work

A correctly sized system, matched to the room through a proper heat load calculation, will generally run more efficiently than one that's undersized and constantly working at maximum capacity, or oversized and cycling on and off repeatedly. Both extremes tend to cost more to run than a well-matched system.

This is one of the main reasons we carry out a survey before quoting for installation, rather than picking a unit based on room size alone.

How the building holds temperature

Insulation, glazing and orientation all affect how much work a system has to do to maintain a set temperature. A loft conversion with limited insulation and south-facing glazing will demand far more from its air conditioning on a hot day than a well-insulated ground floor room facing north.

Simple measures like blinds or curtains on sunny windows, and keeping doors closed to unconditioned areas, reduce the load on the system and therefore the electricity it draws.

Set temperature and mode of use

A system set several degrees colder than actually needed doesn't cool a room meaningfully faster, it simply runs for longer and draws more electricity to reach and maintain that lower target.

Habits that make a noticeable difference

• Setting a moderate target temperature rather than the coldest setting available
• Using timer functions so the system isn't running in an empty room
• Relying on fan-only mode when a room just needs air movement, not full cooling
• Closing internal doors so conditioned air isn't lost to unheated or uncooled spaces
• Keeping filters clean so the system doesn't have to work harder to move air

Heating mode versus cooling mode

Most modern residential and commercial systems are heat pumps that can run in reverse to provide heating as well as cooling. Used sensibly, heating mode can be an efficient way to warm a room, particularly during milder parts of the year, because heat pumps move heat rather than generating it directly from electricity.

Running any heating system, air conditioning included, at very low outside temperatures increases the work the system has to do, so efficiency naturally drops off in the coldest months compared with a mild autumn evening.

The effect of poor maintenance on running costs

A neglected system with a dirty filter, restricted outdoor unit, or reduced refrigerant charge has to work harder to deliver the same result, which shows up as higher electricity use over time even before the system fails outright. Regular servicing is one of the more direct ways to keep running costs in check, because it catches these issues before they become expensive.

Comparing running costs to alternatives

It's worth comparing air conditioning running costs against whatever it would otherwise replace, such as portable fans and electric heaters used together, or an ageing gas boiler system for heating. Air conditioning used as a heat pump can be a genuinely efficient way to heat a well-insulated room, though this depends heavily on the specific property and how it's used, so it's not a claim we'd make without a proper survey of your situation.

What we can and can't tell you

We won't quote a specific running cost figure, because it depends on too many variables specific to your property, your tariff and how the system is used. What we can do is size a system correctly for your space and explain, during the survey, roughly how it's likely to behave so you can make an informed decision.