Air source heat pumps come up in almost every conversation about home heating now, largely because of the grant available through the Boiler Upgrade Scheme. This guide explains how they work in UK conditions, what the scheme covers, and — importantly — what you need to check before assuming you qualify.
How an Air Source Heat Pump Works
A heat pump does not generate heat by burning anything. It moves heat from one place to another using a refrigeration cycle — the same physics as your fridge, running in reverse.
It extracts warmth from the outside air, even when that air is cold, compresses the refrigerant to raise its temperature, and releases that heat inside the property. Because it is moving existing heat rather than creating it, a heat pump can deliver several units of heat for each unit of electricity it consumes.
That ratio is the SCOP figure. A well-specified, correctly installed system typically achieves a SCOP of around 3 to 4, meaning three to four units of heat per unit of electricity.
Do They Work in a British Winter?
Yes, and this is worth addressing directly because it is the most common objection.
Modern air source heat pumps extract usable heat well below freezing. Efficiency does fall as the outside temperature drops — the SCOP at -5°C is lower than at 7°C — but the system continues to work. Heat pumps are standard domestic heating across Scandinavia, where winters are considerably harder than ours.
What genuinely matters for performance in a UK home is less about the weather and more about the building:
- Insulation and draughtproofing. A heat pump delivers heat at a lower flow temperature than a gas boiler, so a poorly insulated house will feel the difference. Insulation work often pays for itself before the heat pump does.
- Emitter sizing. Lower flow temperature means existing radiators may need upsizing, or underfloor heating suits better.
- Correct system design. An undersized or badly commissioned heat pump is the usual cause of the disappointing stories you read about.
The Boiler Upgrade Scheme
The Boiler Upgrade Scheme (BUS) is a UK Government grant, administered by Ofgem, that contributes towards replacing a fossil fuel heating system with a heat pump in England and Wales.
Check the current position before relying on this. Grant amounts, eligibility criteria and scheme end dates have all been revised since the scheme launched. Confirm the current terms on the GOV.UK Boiler Upgrade Scheme page before making a decision. Scotland and Northern Ireland operate separate schemes.
How the scheme works in practice
- The grant is claimed by the installer, not the homeowner. It is deducted from your quoted price rather than paid to you.
- The installer must be MCS certified for heat pump installation. This is a specific accreditation, separate from F-Gas certification.
- The property normally needs a valid EPC with no outstanding recommendations for loft or cavity wall insulation.
- The system being replaced must be a fossil fuel system — typically gas, oil or LPG.
- There are eligibility conditions around property type and existing heating that are worth checking against your specific situation.
Being straight with you about what we do. Tempest Air Conditioning is F-Gas certified and REFCOM registered for air conditioning installation, repair and servicing. We are not currently MCS certified, which means we cannot install a heat pump under the Boiler Upgrade Scheme or claim the grant on your behalf.
If a BUS-funded heat pump is what you are after, you need an MCS-registered installer — you can find one through the MCS website. We would rather tell you that now than waste your time. If you want air conditioning, or a comfort-cooling system that also heats, that is exactly what we do.
Air Conditioning as Heating
Worth knowing: most modern wall-mounted split air conditioning systems are themselves air source heat pumps. They will heat a room efficiently as well as cool it.
This is not the same thing as a whole-house heat pump replacing your boiler and running your radiators and hot water. But for a home office, a conservatory, a loft room or any space your central heating struggles with, a split system used in heating mode is often a genuinely efficient answer — and it gives you cooling in summer from the same unit.
- No grant applies, because it is not a full heating system replacement.
- No MCS certification is needed, because it is an air conditioning installation.
- Running costs in heating mode are typically well below electric resistance heaters.
Talk to Us About Cooling and Comfort Heating
If you want a room that is comfortable in July and usable in January, a split system will do both. Tell us about the space and we will advise on what suits it.
