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Air source heat pumps UK

What is an air source heat pump?

Air source heat pumps take heat from outside air and move it into the home for heating and, in many properties, hot water. The important checks are how the system is arranged, whether cooling is realistic, and whether the home actually suits that route.

Energy Saving Trust and MCS both describe the common domestic route as heat taken from outside air and transferred into a wet heating system for radiators, underfloor heating, and often hot water. That is why air source heat pump systems need more than a product brochure to judge them properly. · 4 min read

ASHP survey reports Heat pump survey route

For site checks, see the air source heat pump survey guide. For electricity use and operating cost, see the ASHP running costs UK guide.

Basics

Air source heat pump systems move heat, they do not create it from scratch

How it works

The outdoor unit extracts heat from external air, even when it feels cold outside. That heat is upgraded and used inside the property instead of being created directly by burning fuel on site.

System layout

Most domestic air source heat pump systems are tied to emitters, pipework, controls, and often a hot-water cylinder. That means the success of the install depends on more than just outdoor-unit placement.

What it is not

It is not the same as an air-to-air system. Air-to-air routes deliver warm or cool air directly through indoor units instead of feeding a wet emitter network.

Suitability

The result depends on heat loss, emitters, hot water, siting, and electrical reality

Fabric and demand
  • Heat-loss assumptions need to be credible
  • U-value defaults can change the design conversation fast
  • Poor evidence creates false confidence early
Emitters and hot water
  • Existing radiators may or may not be enough
  • Cylinder layout and plant-room reality still matter
  • The system route has to fit how the home is actually heated
Outside and electrical
  • Outdoor-unit siting is never just a sketch problem
  • Noise, route length, access, and neighbour context matter
  • Electrical context can make a simple idea more complex on site
Cooling

Some air source heat pumps can cool, but not every home should expect the same result

Possible

Some air source heat pumps can provide cooling, but that depends on the system design, controls, and the indoor heat-delivery route. It is not a universal promise built into every domestic setup.

Wet-system reality

A standard air-to-water setup designed around radiators and hot water is a different answer from a system designed with cooling in mind. Homes that want cooling need that question raised early, not added as an afterthought.

Why it matters

This is one of the biggest reasons to separate air source heat pumps from air-to-air routes. The headline technology sounds similar, but the way the home is heated or cooled can be very different.

Advantages

The advantages only count when the system suits the home

Why people choose them

Air source heat pump advantages usually centre on lower-temperature heating, electrification, and the chance to move away from oil or gas. Those are real benefits when the system is designed honestly.

Where they fall down

Weak heat-loss assumptions, undersized emitters, poor siting, or electrical constraints can turn a good idea into a compromised job. The technology does not rescue bad inputs.

What helps

A stronger survey, clearer heat-loss evidence, and a realistic view of the system layout do more for air source heat pump performance than generic claims about efficiency ever will.

Use the next route

Pick the page that matches the decision you are making now

ASHP survey reports Air source heat pump survey ASHP running costs UK ASHP vs air-to-air ASHP efficiency guide ASHP calculator guide Heat loss calculations
FAQs

Questions people ask about air source heat pumps

An air source heat pump takes heat from outside air and transfers it into the home for heating and, in many cases, hot water.

The outdoor unit extracts heat from the air, upgrades it through the refrigeration cycle, and then delivers that heat through the indoor system, controls, and emitters.

Some can, but not every home or system is designed for that outcome. Cooling depends on controls, system layout, and whether it was considered early enough.

No. Air-to-water ASHP systems usually feed a wet heating network, while air-to-air systems condition the air directly through indoor units.

Use the air source heat pump survey page when the system type is already clear and you want the exact survey checklist before pricing or design starts.

Official reference points

What the consumer-facing guidance agrees on

Heat source

Energy Saving Trust and MCS both describe an air source heat pump as a system that takes heat from the outside air and upgrades it for use inside the home.

Typical domestic route

The usual domestic route is air-to-water: the heat pump feeds radiators or underfloor heating and can also heat stored domestic hot water.

What that means

That official description is why survey work has to cover the wet system properly. Emitters, cylinder space, heat loss, siting, and electrics are part of the same answer.

Sources checked on 17 April 2026: Energy Saving Trust: air source heat pumps, Energy Saving Trust: heat pumps guide, and MCS: air source heat pump.