Are you thinking about switching from your gas boiler but aren’t quite sure how a heat pump actually keeps your home warm? This article is for you. We break down exactly how heat pumps work, which type might suit your home, and what you need to know before making the switch.
At the simplest level, a heat pump doesn’t create heat the way a boiler does. Instead, it moves existing heat from the outside air or the ground into your home. Because it transfers heat rather than burning fuel, it can deliver more heat energy than it uses in electricity. That efficiency is the main reason heat pumps are becoming a core part of the UK’s shift to low-carbon heating.
But to understand how a heat pump would work in your home and whether it’s a good swap for your boiler, it helps to understand what the machine actually does.
Why understanding heat pumps matters if you’re considering a switch
Most homeowners who ask about heat pumps want clarity on three things:
Will it actually keep my home warm?
Will it cost more or less to run?
Will my home need upgrades before a heat pump works properly?
Unlike a boiler, a heat pump delivers gentle, continuous heat. This is why it feels unfamiliar at first. The system isn’t designed to fire on and off in short bursts. Instead, it runs longer and maintains a stable, comfortable temperature in the background. Keep it running all day, not just when you get home from work. Once you understand that shift, the whole system starts to make more sense.
How a heat pump works (in plain English)
A good way to picture a heat pump is to think of a fridge working in reverse. Your fridge extracts heat from inside the fridge compartment and sends it out into the room. A heat pump does the same, except it takes heat from outside your home and moves it indoors.
It begins with the outdoor unit, which contains a refrigerant that evaporates at very low temperatures. Even on cold days, the air holds some thermal energy. As the refrigerant passes through the outdoor coil, it absorbs this low-grade heat and changes from a liquid into a gas.
The heat pump then compresses this gas. Compressing a gas increases its temperature, so the refrigerant becomes hot enough to be useful. This hot refrigerant flows into the indoor unit, usually connected to your radiators or underfloor heating. There, it releases its heat through a heat exchanger, warming the circulating water in your system.
Once it has given up its heat, the refrigerant cools down, condenses back into a liquid, and heads back outside to start the cycle again. This loop can run for hours at a time. That’s normal, and it’s also why heat pumps feel different from boilers. Boilers burn fuel to create short bursts of high heat. Heat pumps supply a steady flow of mild heat, which is more efficient but requires a different mindset from the user.
Air-source vs ground-source: which suits your home?
Airsource heat pump
Most UK homes use an air-source heat pump because it’s simpler to install and fits well into suburban and urban settings. It sits outside, looks a bit like an air-conditioning unit, and draws heat from the air. Today’s models work reliably in cold weather, and many homes can be retrofitted without major disruption.
Ground source heat pump
A ground-source heat pump does the same job but gathers heat from the soil instead of the air. The ground stays at a more constant temperature year-round, which makes these systems more efficient. However, they require either long trenches for horizontal pipe loops or a professionally drilled borehole. That makes ground-source systems more expensive and better suited to rural homes, large plots, or properties undergoing major renovations.
For most households, the deciding factors are cost, garden space, and how much disruption you’re comfortable with. Both types work extremely well when properly designed.
Is your home suitable for a heat pump?
Suitability isn’t about the age or style of your home, it’s about how well it holds heat. If your home already warms up easily and stays warm once heated, a heat pump will often perform well.
Houses with solid loft insulation, reasonable wall insulation, and modern double glazing tend to be a good fit. If you’ve ever noticed that your home cools down quickly when the heating turns off, that’s usually a sign that insulation improvements will help, whether you choose a heat pump or not.
Radiators also matter. Heat pumps run on lower flow temperatures than gas boilers, so they work best with radiators that have enough surface area to release that gentler heat. In many homes, that means replacing a few smaller radiators with larger equivalents. It’s not a full re-pipe; it’s usually a targeted upgrade.
Finally, you’ll need space for a hot water cylinder. Heat pumps don’t produce instant hot water the way a combi boiler does, so they store it instead. Most homes can find space for one, an airing cupboard, a utility area, or even a loft with suitable support.
None of these requirements are unusual or extreme. They’re simply different from what a gas boiler needs.
What you should know before making the switch
A successful heat pump installation always starts with a heat-loss survey. This measures how much heat your home loses through the walls, roof, windows, and floors. It’s the foundation of a properly sized system. A heat pump that’s too small will run constantly but never quite satisfy the thermostat; one that’s too large will short-cycle and reduce efficiency. A good installer will model this carefully.
Your home’s insulation is just as important as the heat pump itself. Improving loft insulation, topping up cavity walls, and sealing draughts can make the difference between a system that feels brilliant and one that feels underwhelming. Think of insulation as part of the heating system.
Running costs depend on efficiency. The more heat you get out per unit of electricity, the better the economics look. Heat pumps are often cheaper to run than oil, LPG, or direct electric heating. Compared with gas, it varies by household. Well-insulated homes with steady heat patterns tend to see the most benefit; homes with poor insulation may find running costs creep up without some fabric improvements.
Do you need help finding a heating engineer?
Share a few details about your home, and our UK Property Looker assistant will point you towards qualified heating engineers who can assess your property and give a professional view on whether a heat pump is a good fit.
Find a heating engineer →
Good to know
There’s the Boiler Upgrade Scheme, which offers £7,500 off the cost of a heat pump in England and Wales if you use an MCS-certified installer. That subsidy makes a significant difference to the overall cost.
The bottom line: warm, steady heat with lower carbon
A well-installed heat pump doesn’t blast heat the way a boiler does. Instead, it keeps your home warm all day with low, steady output. Many people find that their homes feel more consistently comfortable because there are no highs and lows, just a stable temperature.
You also gain a system with a long lifespan, fewer moving parts, and dramatically lower carbon emissions. For many households, especially those with decent insulation, it’s one of the cleanest and most efficient ways to heat a home today.
One reflective question
If your home stayed warm all day for less energy, would you still think of heating as something that needs to be “switched on and off,” or could it simply become background comfort?