How Much Does Air Con Cost To Run In The UK 2026 Guide

UK heat is on the rise. More homes now look to air con for cool air. But one big ask stays the same: how much will it cost to run?

In most UK homes, air con will cost from 20p to 70p per hour. The true cost will rest on unit size, rate per kWh, and how you use it.

Key Facts

20p–70p

Typical cost per hour for most UK homes

kW × p

The formula: unit size × your electricity rate

SEER

Higher SEER rating = lower running cost

Split

Split wall units cost less to run than portable ones

How To Work Out Your Run Cost

You need two figures: your unit size in kW, and your electricity rate in pence per kWh.

The Formula

kW × p per kWh = cost per hour

2.5 kW unit at 25p per kWh

2.5 × 25p = 62.5p/hr

5 kW unit at 25p per kWh

5 × 25p = £1.25/hr

What Can Change The Cost

Six factors affect how much you actually pay per hour.

01 · Unit Type

Split vs Portable

Split wall units use inverter tech to shift load, not blast full time. Much more efficient.

02 · Unit Size

Right Sizing

A big lounge needs more kW than a small bedroom. Too big or too small both waste cash.

03 · SEER Rate

Efficiency Score

SEER is a score of cooling skill. High SEER means less power for the same cool air.

04 · Home Insulation

Keeping It In

Good loft, wall seal, and glass holds cool air in. Bad draught lets hot air in.

05 · Use Habits

How You Run It

Low set temp, long run time, and open doors raise cost. Sleep mode cuts it.

06 · Electricity Plan

Your Rate Per kWh

Your rate per kWh is a big part of the sum. A cheaper tariff cuts cost straight away.

Split vs Portable Units

Type	Run Cost	Upfront Cost	Long Term
Split Unit	Lower	Higher	Best value
Portable Unit	Higher	Lower	More per hour

Split units cost more to buy, but tend to cost less each hour. Portable units are cheap to buy but use more power over time.

Four Ways To Cut Run Cost

Use Smart Settings Set a timer and temperature with care. Don't run it colder than you need.

Clean The Filter Dust slows air flow and makes the unit work harder. Clean it every few weeks.

Block Peak Sun Close blinds during the hottest part of the day. Less heat in = less work for the unit.

Buy High SEER The best long-term move. A high SEER unit pays for the difference in efficiency over time.

Is Air Con Expensive To Run In The UK?

Not as expensive as most people fear. A new split unit, used with care, costs roughly the same per hour as running a washing machine or tumble dryer.

For many homes, the ability to sleep well and work comfortably through hot weeks is worth that cost.

Frequently Asked Questions

Is it cheaper to leave it on all day?

With modern inverter units, a low steady run can cost less than blasting from hot each time. But it depends on your home and how well it holds temperature.

Does heat mode cost more?

Heat mode can use more power, but as a heat pump it can still beat old electric bar heaters on efficiency — especially in mild cold.

How much does a 5 kW unit cost per hour?

At 25p per kWh, it costs around £1.25 per hour at full load. In practice, inverter units rarely run at full load continuously.

Ready To Work Out Your Cost?

Pick the right size. Check the SEER rating. Use smart settings. With those three things in place, you can stay cool without bill shock.

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