Heat Pump vs Gas Boiler: Which Uses Less Energy?
A heat pump generally uses less purchased energy than a gas boiler to provide the same amount of heat, because it moves heat rather than making all of it by burning fuel. The exact difference depends on the heat pump’s seasonal efficiency, the boiler’s efficiency, and how the home is heated.
What “uses less energy” means
A fair comparison starts with the same useful heat delivered to the rooms, not just the energy entering each appliance. A boiler burns gas and loses some heat through its flue and other inefficiencies. A heat pump uses electricity to transfer heat from outdoor air, the ground, or water into a building. It therefore can deliver several units of heat for each unit of electricity it consumes.
This comparison is about energy consumption, not necessarily running cost, emissions, or suitability. Electricity and gas have different prices, and their environmental impact depends on how they are generated and supplied. A heat pump can use less energy while costing more to run in a particular place if electricity is comparatively expensive.
How a heat pump and boiler work
A heat pump circulates refrigerant through a cycle of evaporation, compression, condensation, and expansion. The refrigerant absorbs heat outside, is compressed to raise its temperature, and releases heat into the home’s heating system. Even cold outdoor air contains thermal energy, though extracting heat becomes more challenging as the outdoor temperature falls.
A gas boiler burns natural gas to heat water, which is circulated through radiators or underfloor heating. Some combustion energy leaves with exhaust gases, and additional losses can occur while the boiler cycles or when hot water sits in pipes. Modern condensing boilers can recover some heat from exhaust gases, particularly when return water is cool enough for condensation.
Efficiency: COP and seasonal performance
Heat-pump efficiency is commonly described by the coefficient of performance (COP): useful heat delivered divided by electricity used over a stated period. A COP of 3 means 3 kWh of heat for each 1 kWh of electricity under those measured conditions. It is not a claim that the machine creates energy; the extra heat is transferred from the environment.
Because conditions vary, a single test-point COP is not the whole story. Seasonal performance figures account for changing outdoor temperatures and operating conditions over a heating season. The precise metric and test method vary by region, so compare like-for-like product data and consider the expected performance in your climate and building.
For a boiler, useful efficiency is the heat delivered divided by the gas energy consumed. If a boiler is 90% efficient on the relevant basis, it delivers about 0.9 kWh of useful heat per kWh of gas energy. Efficiency figures may use different conventions, including whether fuel energy is measured on a higher or lower heating-value basis, so avoid comparing numbers without checking their definitions.
A simple energy comparison
Suppose a home needs 10,000 kWh of useful heat over a season. If its heat pump achieves a seasonal COP of 3, it would use roughly 3,333 kWh of electricity: 10,000 ÷ 3. If a gas boiler operates at 90% efficiency on a comparable basis, it would use roughly 11,111 kWh of gas: 10,000 ÷ 0.9.
These are illustrative calculations, not predictions for a particular home. They compare energy at the appliance and do not include upstream energy used to generate electricity or deliver fuel. They also do not establish which option costs less; that requires local energy prices and, for a full household comparison, the system’s actual seasonal performance.
What changes real-world energy use?
A heat pump’s seasonal performance depends on the temperature it must deliver. Lower-temperature water generally allows it to work more efficiently. A well-insulated home with appropriately sized radiators or underfloor heating may be able to stay comfortable with lower flow temperatures. A poorly insulated building or undersized emitters may require hotter water, which can reduce efficiency.
- Outdoor conditions: Cold weather can lower heat-pump output and efficiency; some systems use supplementary resistance heating in demanding conditions.
- System design: Correct sizing, commissioning, controls, and refrigerant-system condition all affect performance.
- Heating pattern: Heat pumps are often most effective when run steadily at lower temperatures. Frequent deep setbacks or rapid high-temperature recovery can affect consumption, though suitable controls depend on the system and household.
- Building heat loss: Insulation, draughts, ventilation, and the desired indoor temperature determine how much heat either system must supply.
- Hot water: Domestic hot-water demand and the temperature needed for it can influence overall seasonal performance.
Boiler use also varies with boiler condition, controls, operating temperature, cycling, and distribution losses. A poorly configured boiler may perform worse than its published rating, just as an unsuitable heat-pump installation may fail to achieve expected seasonal efficiency.
Energy use, bills, and emissions are different comparisons
Less energy does not automatically mean a lower bill. To estimate heating cost, multiply the electricity used by the electricity price, or the gas used by the gas price, using comparable units and including any relevant standing charges only when comparing total bills. Because tariffs and charges vary, there is no universal cost winner.
Emissions are a separate question. A heat pump’s operational emissions depend on the electricity mix; a gas boiler emits carbon dioxide when it burns gas. A broader lifecycle comparison may also consider equipment manufacture, fuel supply, and electricity generation. Results vary by location and assumptions, so energy efficiency alone cannot provide a complete emissions figure.
Choosing between the systems
Start with the building’s heat demand and the system’s likely seasonal performance, rather than comparing headline efficiency claims alone. A qualified heating professional can assess heat loss, existing emitters, hot-water needs, electrical capacity, outdoor-unit location, and whether improvements to insulation or controls would help.
- Ask for a heat-loss assessment and a design matched to the home.
- Check expected seasonal performance at the intended flow temperature and local climate.
- Compare delivered heat, energy use, and running costs separately.
- Consider noise, space, electrical work, hot-water arrangements, and maintenance needs.
- For a boiler, check its actual condition, controls, and whether it is operating efficiently at suitable temperatures.
A heat pump is not automatically the best choice for every property, and a gas boiler is not automatically the lower-energy option because it can produce high-temperature water quickly. The useful comparison is between properly designed systems that provide the same comfort and hot water in the actual building.
Frequently Asked Questions
Does a heat pump use less electricity than a boiler?
A gas boiler uses gas rather than electricity for most of its heating, although its controls and pumps use some electricity. The better comparison is total energy input: a heat pump typically needs fewer units of purchased energy to deliver the same useful heat, but that energy is electricity while the boiler’s is gas.
How much more efficient is a heat pump?
There is no single fixed percentage. Divide useful heat by electricity for the heat pump, and useful heat by gas input for the boiler, using seasonal figures on compatible measurement bases. A seasonal COP of 3 and a 90% boiler efficiency, for example, give the illustrative energy comparison above.
Do heat pumps work in very cold weather?
Air-source heat pumps can extract heat in cold weather, but their output and efficiency generally decline as outdoor temperatures fall. Suitability depends on the model, climate, building heat loss, system design, and whether backup heat is needed.
Is a heat pump always cheaper to run than a gas boiler?
No. Running cost depends on seasonal performance and local electricity and gas prices. A heat pump may use less energy but still have a higher bill where electricity costs much more per unit than gas.
Will existing radiators work with a heat pump?
Sometimes. The answer depends on radiator size, room heat loss, and the water temperature needed on cold days. An assessment can identify whether existing radiators are adequate, need adjustments, or should be replaced.
Related
Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.