Choosing between a heat pump and a boiler is not simply a comparison of two equipment prices. The cheaper system is usually the one that delivers the right amount of usable heat for your home at the lowest total cost, including installation, energy, maintenance and eventual replacement.
A gas boiler can be inexpensive to install and may provide predictable heat for an older, poorly insulated property. A heat pump can reduce heating consumption substantially, but its performance can be restricted by cold weather, a large heat-loss area, high electricity prices or unsuitable radiators.
This comparison explains the factors to review before you invest. It is intended to help you prepare for a quotation and ask suppliers for comparable information.
What is the difference between a heat pump and a boiler?
A boiler burns fuel, usually natural gas or heating oil, to heat water. The water then flows through radiators or a cylinder, while a combi boiler also provides domestic hot water. A heat pump does not create heat by burning fuel. It uses electricity to move heat from outside a property, or from the air, ground or water, into the home.
That distinction matters because the energy required to operate each system is different. A boiler is efficient at producing heat around the point of use, but some energy is lost in the process. A heat pump uses electricity to move several units of heat for each unit of electricity consumed, subject to the temperature required and the conditions outside.
Heat pumps are commonly air-to-water, ground-to-water or water-to-water systems. An air-source heat pump is usually the simplest option for a typical home because it does not require groundworks. It still needs an outdoor unit, an indoor cylinder in many cases, controls, pipework and emitters designed to work at lower flow temperatures.
Which system costs more to install?
The installation cost of a heat pump is often higher than that of a standard boiler replacement. The difference can include the cost of a cylinder, low-temperature radiators, additional controls, electrical work, pipework changes and a new emitter system. A boiler may be a lower initial cost when you already have a suitable gas supply and a complete heating system.
However, replacing an old boiler with a new one is not always a direct like-for-like comparison. A new boiler may require a larger system upgrade, new pipework, additional radiators, a larger cylinder or electrical work. Conversely, a heat pump installation may avoid replacing a failed boiler and can be designed to support future energy upgrades.
Use the same scope when requesting quotations. Ask each installer to state whether the price includes the heat pump, cylinder, controls, radiators, pipework, electrical upgrades, commissioning, warranty and any necessary building work. A lower headline price can become more expensive if essential components are excluded.
How much do heat pumps and boilers cost to run?
Running costs depend on the price of gas and electricity, the system’s efficiency, the weather and how well the property is insulated. The following table shows an illustrative comparison. The figures are not a quote for a specific home; they demonstrate how a cost calculation can work.
| Factor | Heat pump | Gas boiler | What affects the result? |
|---|---|---|---|
| Energy source | Electricity | Natural gas or oil | Local tariffs and fuel availability |
| Useful efficiency | Often around 2.5–4 units of heat per unit of electricity, depending on conditions | Typically around 85–92% for a modern condensing boiler | Model, weather and return-water temperature |
| Annual heating demand | Lower after heat-loss improvements | Higher if the building remains poorly insulated | Fabric, ventilation and hot-water use |
| Typical annual energy cost | Can be lower where heat demand is low and electricity is economical | Can be lower where gas is very cheap and the home has high heat loss | Tariffs, usage, climate and system design |
| Maintenance | Cleaning filters, checking refrigerant and servicing the unit | Annual servicing and occasional repairs | Manufacturer guidance and equipment age |
For a simple comparison, estimate the energy needed for space heating and hot water, divide it by the system’s expected efficiency, and multiply by the unit price of electricity or gas. Then add standing charges, maintenance and any planned replacement cost. Use your actual bills where possible rather than relying on a national average.
To see how this works in practice, consider a standard home with an annual space heating and hot water demand of 12,000 kWh. An A-rated condensing gas boiler operating at 88% seasonal efficiency requires roughly 13,636 kWh of gas input. At a gas tariff of 7p per kWh, the annual fuel cost totals approximately £955, alongside typical annual servicing costs of £80 to £120.
By contrast, an air-source heat pump delivering the same 12,000 kWh of thermal energy with a Seasonal Coefficient of Performance (SCOP) of 3.4 will consume approximately 3,529 kWh of electricity across the year. If electricity is priced at 27p per kWh, the annual operating cost comes to around £953, with annual maintenance inspections generally running between £100 and £180. If fabric improvements allow the flow temperature to drop from 50°C to 35°C, increasing the SCOP to 4.0, the electricity demand falls to 3,000 kWh, reducing the annual running expense to roughly £810.
System efficiency drops if the heat pump must operate at higher flow temperatures (such as 55°C to 65°C) to compensate for undersized radiators, compared to an optimal low-temperature design running at 35°C to 45°C. A boiler’s efficiency is comparatively stable, although fuel consumption rises significantly when structural heat loss is unaddressed.
When is a boiler likely to be the cheaper choice?
A boiler may be the more practical and less expensive option when a property has an existing gas connection, limited electrical capacity, high space-heating demand or a heating layout that requires a high water temperature. It can also be sensible where a heat pump would require extensive fabric improvements, replacement radiators and significant electrical upgrades.
Boilers are particularly relevant for homes that are difficult to insulate without major disruption. A heat pump is most efficient when it can supply water at a moderate temperature. If radiators are undersized, the system may need to run hotter than intended, increasing electricity use.
A modern condensing gas boiler can be a suitable short-term replacement when the existing home is already well insulated and the property is connected to a low-cost gas supply. Its operating cost will still depend on the tariff. A low purchase price does not remove the effect of future gas-price increases.
When is a heat pump likely to be cheaper?
A heat pump is more likely to be the cheaper long-term option where the home has good insulation, a low heat-loss rate, space for the outdoor unit and a suitable electrical supply. Low flow temperatures are important. Underfloor heating, oversized radiators and carefully sized emitters can allow the heat pump to operate efficiently without wasting energy.
The property’s location and climate also matter. A heat pump in a mild area may need less heating and can operate efficiently for more of the year. In a colder region, backup heating or a system designed for lower temperatures may be necessary. Avoid a quotation that assumes the heat pump will cover every load without explaining how peak demand and hot water are handled.
Heat pumps can also be paired with solar electricity. This does not automatically make the system free to run, but it may reduce the amount of grid electricity purchased during sunny periods if your tariff and system controls support the arrangement. Battery storage, export tariffs and timing charges should be evaluated separately.
What should be included in a whole-house comparison?
Before comparing savings, ask for a room-by-room heat-loss assessment. A heat-loss calculation can show how much insulation, glazing or air sealing is needed. It can also identify rooms that may require smaller radiators or other design changes. Improving the building first can reduce both the equipment size and the lifetime energy cost.
Review ventilation at the same time. Insulating an airtight home without providing adequate controlled ventilation can lead to moisture problems and poor indoor air quality. The correct approach may involve continuous mechanical ventilation, extract ventilation or a balanced system, depending on the property.
Request a written comparison covering:
- Installed price, including financing and any building work.
- Annual space-heating and hot-water estimates.
- Electricity and gas tariff assumptions.
- Expected efficiency and weather assumptions.
- Maintenance, servicing and parts availability.
- Equipment warranty and expected replacement interval.
- Grants, rebates or tax incentives available in your area.
- The effect of future insulation or glazing work.
Do not compare a heat pump with a boiler using only a fuel-cost figure. A fair comparison needs the same heating demand, the same comfort level, the same hot-water requirement and the same ownership period.
How long does payback take?
Payback is the time needed for lower operating costs and incentives to offset the higher purchase or installation cost. A heat pump may take several years to recover its additional cost, while a boiler replacement may have little or no financial payback if it is a basic replacement of an existing system.
The payback period can change considerably if electricity prices rise, gas prices fall, grants change or your home requires more heating than expected. A sensitivity analysis is useful. Ask the installer to show how the result changes if electricity costs increase by 10 percent, the home uses more heating or the heat pump operates at lower winter efficiency.
Consider lifetime value rather than only the first winter. Heat pumps may have a long service life with regular maintenance, but compressors, controls and other electrical components can eventually need repair. Boilers also have a finite life and require reliable annual servicing. Keep a separate allowance for replacement so the comparison reflects the full ownership period.
Homeowners comparing energy efficiency upgrades can benefit from reviewing the building before selecting heating equipment. A heat-loss and ventilation assessment often provides more useful guidance than equipment marketing alone.
Practical steps to make the decision
Start with your last two or three years of energy bills. Record annual gas or oil use and electricity use, especially the winter periods. Note the type of property, floor area, glazing, insulation, hot-water demand and the age of the current boiler.
Then obtain at least two detailed heating proposals. Specify the heat-loss assumptions, desired room temperature and hot-water usage. Check that each proposal explains why the proposed radiators, cylinder and controls are suitable.
Ask for the calculated annual operating cost over 10, 15 and 20 years. Include maintenance, planned repairs and any replacement reserve. This makes it easier to see whether a higher installation cost is offset by lower energy use, or whether a simpler boiler solution better fits the property.
If you are planning a wider project, you can discuss your property and upgrade priorities with a home energy adviser before committing to a heating system.
In many homes, a heat pump is cheaper to operate after the building has been improved and the emitters have been sized correctly. A boiler can still be the more cost-effective choice where a gas connection already exists, electrical upgrades are limited or the property needs a high-temperature system. The strongest decision is based on measured heat demand, transparent installation costs and a realistic comparison of lifetime energy use.
Evaluating heat pumps and boilers for your home? Consider consulting a qualified heating designer or energy adviser. They can help you review heat loss, system design, installation costs and expected running expenses before you select an option.
