How much does an air-to-air heat pump cost to run?

The short answer

For heating, an air-to-air heat pump is usually one of the cheapest ways to heat a room with electricity, because it delivers several units of heat for each unit of electricity it uses. For cooling, it’s new electricity use if you have nothing today, but it’s typically far more efficient than a portable air conditioner. What it actually costs you depends on four things: how much heat or cooling the room needs, how efficient the unit is, how many hours it runs, and what you pay for electricity.

How to work it out

The sum is simple:

Running cost per hour = (heat or cooling delivered ÷ efficiency) × your electricity price

Efficiency for heating is the COP (coefficient of performance): a COP of 3.5 means 3.5 kW of heat for every 1 kW of electricity. Over a whole season it’s quoted as SCOP. For cooling the equivalents are EER and SEER. Efficiency is higher in mild weather and lower on very cold or very hot days.

A worked example (heating)

These figures are illustrative assumptions, not a quote. Check your own tariff.

• A bedroom needs 2 kW of heat to stay warm on a cold evening
• The heat pump runs at a COP of 3.5 in those conditions
• Electricity costs 25p per kWh

Electricity used: 2 ÷ 3.5 = about 0.57 kW, so roughly 14p an hour. A plug-in electric heater producing the same 2 kW uses 2 kW of electricity, about 50p an hour at the same price. That gap is why an air-to-air heat pump suits rooms currently heated by electric heaters.

Against gas central heating the comparison is closer, because gas costs less per unit than electricity. Where an air-to-air system often saves money alongside gas is by heating only the rooms you’re using, rather than running the whole system to warm one cold office.

A worked example (cooling)

Same caveats. A bedroom needs 2 kW of cooling on a hot afternoon; the unit runs at an EER of 3; electricity is 25p per kWh. Electricity used: 2 ÷ 3 = about 0.67 kW, roughly 17p an hour. If it runs for three hours on 20 hot evenings a year, that’s about £10 for the summer. Cooling a whole floor all summer is a very different number, which is why we ask how you’d actually use it.

What pushes the cost up or down

• The room: insulation, glazing and sun. A loft room under a warm roof needs more cooling than a shaded study.
• Sizing: an undersized unit runs flat out and struggles; an oversized one cycles on and off. Both waste energy.
• How you use it: a steady setpoint is usually more efficient than blasting it on and off. Timers and schedules help.
• Your tariff: a cheaper overnight rate, or solar panels in summer, can bring cooling costs right down.
• Maintenance: clean filters keep efficiency up. It takes minutes.

What we’d do for your home

We look at the rooms, how you’d use them and your tariff, and give you a realistic running-cost range alongside the price. Not a headline saving. Start your home assessment, or read about air-to-air heat pumps and what affects the installation price.

Sources

• Energy Saving Trust: Air to air heat pumps
• Ofgem: Energy price cap (current unit rates)