If you’ve been hearing a lot about heat pumps but aren’t quite sure what one actually is or whether it makes sense for your home, this guide will give you a straight answer.
No jargon, no sales pitch — just a clear explanation of how the technology works and what it means in practice for a Scottish household.
What Is an Air Source Heat Pump and How Does It Heat Your Home?
An air source heat pump is a heating system that extracts heat from outdoor air and transfers it inside your home to provide central heating and hot water. It doesn’t burn any fuel.
Instead, it uses a small amount of electricity to move heat that already exists in the outside air — even when that air feels cold — into your home’s radiators, underfloor heating, and hot water cylinder.
The simplest way to think about it: a fridge works by removing heat from inside and pushing it out the back. A heat pump does exactly the same thing in reverse.
How Does an Air Source Heat Pump Work Step by Step?
The process is more straightforward than it sounds:
- The outdoor unit draws in outside air, passing it over a coil filled with refrigerant
- The refrigerant absorbs heat from the air and evaporates into a gas — this happens even at temperatures well below freezing
- The gas is compressed, which raises its temperature considerably
- That heat transfers into your home’s heating system, warming your radiators and hot water, while the refrigerant cools back to liquid and the cycle repeats
The electricity consumed powers the compressor and fan — not the heat generation itself.
That’s why heat pumps produce 3 to 4 units of heat for every 1 unit of electricity used, making them up to 400% efficient. No gas boiler, oil boiler, or electric heater comes close to that figure.
Air-to-Water vs Air-to-Air Heat Pumps: Which Type Do You Need?
Air-to-Water Heat Pumps
This is the type most relevant to Scottish homeowners. It connects to your wet central heating system — radiators, underfloor heating, or a combination — and provides domestic hot water too. If you’re replacing a gas or oil boiler, this is almost certainly what you’d be installing.
Air-to-Air Heat Pumps
These deliver warm air directly into rooms and can also provide cooling in summer. However, they don’t produce hot water, which limits their use as a standalone heating solution in most Scottish homes.
What Does an Air Source Heat Pump System Include?
A standard air-to-water installation has four main components:
- Outdoor unit — mounted on an outside wall or on the ground, housing the fan and refrigerant coil
- Indoor unit — installed in a utility room, garage, or cupboard, housing the compressor and heat exchanger
- Hot water cylinder — stores the hot water the system produces
- Distribution system — your existing radiators or underfloor heating delivering warmth room by room
The outdoor unit is roughly the size of a large air conditioning unit, and the indoor components typically occupy a similar footprint to a standard boiler and cylinder setup.
Frequently Asked Questions About Air Source Heat Pumps in Scotland
Do air source heat pumps work in cold Scottish weather?
Yes. Modern heat pumps operate efficiently down to -15°C to -20°C, well beyond what Scotland typically experiences. We cover cold-weather performance in much more detail in our guide to [the best heat pumps for Scottish homes].
Can an air source heat pump work with existing radiators?
In most cases, yes — though some older properties may need radiators upsized. This is assessed during your survey. Underfloor heating is an ideal pairing. For the full picture, see our guide to [heat pump compatibility and installation].
How long does an air source heat pump last?
A well-maintained system typically lasts 20 to 25 years — comparable to or longer than most boilers.
How much does it cost to run a heat pump in Scotland — and are grants available?
Running costs depend on your property and insulation level, but homes replacing oil or LPG heating tend to see the most significant savings. Scottish homeowners also have access to the Home Energy Scotland Grant of up to £7,500 — and up to £18,000 for rural properties. See our full breakdown in our guide to [are heat pumps worth it in Scotland].
Get a Free Heat Pump Survey From Scotland’s Number One Rated Installer
At The Edinburgh Boiler Company, we carry out a full home survey before recommending any system — taking into account your insulation, existing heating setup, hot water demand, and property layout.
As Scotland’s number one rated heat pump installer, we’ll give you a straight, honest answer on whether a heat pump is right for your home. Book your free survey today and we’ll take it from there.
