A heat pump doesn't generate heat by burning fuel. Instead it moves warmth from one place to another, much like a fridge works in reverse. An air source unit sits outside your home and draws in low-grade heat from the air, even on a frosty morning, and upgrades it to a temperature that can warm your rooms and your hot water cylinder. A ground source version does the same job using pipes buried in the garden, where temperatures stay steadier all year round.
Because it's moving heat rather than creating it, a well-installed heat pump can deliver three or four units of heat for every unit of electricity it uses. That efficiency is the whole appeal, but it also explains why heat pumps suit some properties far better than others. They run at lower flow temperatures than a gas boiler, typically 35 to 55°C rather than 70 to 80°C, which means your home needs to hold onto that heat effectively.
Before you think about which model to buy, it's worth understanding how quickly your home loses heat. A heat pump works hardest in a leaky, poorly insulated property, and that's when running costs creep up and comfort drops. In most UK homes, the priority is the fabric of the building.
If your home is already reasonably insulated, perhaps an EPC rating of C or above, you're in a strong starting position. If it's E or below, it's worth addressing the basics first, both for comfort and to get the best from any renewable heating system.
This is the question that catches most people out. Heat pumps run at lower temperatures, so radiators need to be larger, or you need more of them, to release the same amount of warmth into a room. Many homes upgrading from a gas boiler will need some radiators swapped for wider or deeper models, and occasionally a room will need an extra one.
Underfloor heating is ideal because it provides a large surface area at low temperatures, but it isn't essential. A good installer will carry out a room-by-room heat loss calculation and size each radiator accordingly. Be wary of any quote that doesn't include this, as guessing leads to cold rooms and a system that runs constantly.
Hot water matters too. A heat pump heats water more slowly than a combi boiler, so you'll normally need a cylinder, often 150 to 250 litres depending on household size. If you've been used to hot water on demand, this is a genuine change in how you use your home, though most people adapt within a week or two.
An air source heat pump needs a spot outside with good airflow. A unit is roughly the size of a small wheelie bin and is usually mounted on a wall bracket or a low plinth at ground level. You'll want at least a metre of clear space in front of it and room around the sides, so it can pull air through freely. Tucked into a narrow alley or boxed in by a shed, performance suffers and noise becomes more noticeable.
Ground source systems need more land, typically trenches or boreholes, so they suit larger gardens or rural properties. They cost more upfront but run very quietly and efficiently. If you're in a flat or a home with no outdoor space, a heat pump may simply not be an option, and that's worth knowing early.
Planning permission is rarely an issue in England and Wales for air source units, provided they meet size and noise limits, but it's always worth checking with your local authority, particularly in conservation areas or listed buildings.
Whether a heat pump saves you money depends on three things: how efficient your home is, how the system is set up, and how much you pay for electricity versus gas. A well-designed system in an insulated home often runs at a similar cost to a gas boiler, and considerably less than oil, LPG or direct electric heating.
Set expectations realistically. A heat pump isn't a straight swap for a boiler, and it rewards a thoughtful approach. Get two or three quotes from installers accredited under the Microgeneration Certification Scheme, and ask each one to show you their heat loss calculations.
If your home is insulated to a reasonable standard, has outdoor space for a unit, and you're willing to upgrade a few radiators and add a hot water cylinder, a heat pump is very likely to work well for you. If your property is draughty, has no outside space, or needs extensive insulation first, it's worth tackling those issues before committing.
The best next step is a proper survey rather than a guess. A qualified installer can tell you within an hour or two whether your home is ready, what improvements would help, and what the system would realistically cost to run. For many UK households, a heat pump isn't just a greener choice, it's a genuinely comfortable and practical one.
Low Carbon Living shares practical, down-to-earth guidance on practical low-carbon living and sustainability for uk homes and communities for readers across the UK.
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