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Heat Pumps vs Gas Boilers

Unfortunately, you can’t live in the UK without some sort of heating at home. Winter temperatures in Scotland are often below freezing, and in England and Wales they range between 2 and 7 degrees Celsius (36-45 degrees Fahrenheit).

Gas central heating is the most common way to heat water, but many households are now going for heat pumps. There was a big increase in 2024 in the number of households installing heat pumps, partly due to the increase in the grant under the Boiler Upgrade Scheme (BUS) and the desire to reduce carbon emissions.

Heat pumps are being subsidised by the government, who want them to replace gas boilers as part of their 2050 net-zero target. Heat pumps run on electricity, which the government hopes to produce from renewable energy sources like solar and wind.

What is a Heat Pump?

A heat pump takes air from outside your home and uses it to provide central heating and hot water. It does this by taking the air from the atmosphere.

Then, a refrigerant inside the pump is compressed, which turns into hot gas. The gas heats your home. Once the gas has cooled, it turns back into refrigerant and is ready for the next cycle.

Pros & Cons of a Heat Pump

Pros:

✔ Energy Efficient
✔ Eco-Friendly
✔ Lower running costs in the long term

Cons:

✖ Expensive to buy and install
✖ Less effective in poorly insulated homes
✖ Space needed for the unit and pipework or boreholes if you want a ground source air pump.

There are three types of air pumps, and they are:

Air Source Heat Pumps

Air source heat pumps take the heat from the air around the air pump unit, which looks like an outdoor air conditioning unit.

This type of unit is the most popular because it’s cheaper to install and takes up less space. The pump will heat your home even in temperatures as low as 15 degrees Celsius.

Ground Source Heat Pumps

Ground source heat pumps take the heat from the air underground. To have a ground source heat pump, you’ll need a big garden so you can sink boreholes or run underground pipes. Installation costs are much higher than those of an air source pump because of the excavation work and pipe laying.

Ground source heat pumps are more efficient than air source heat pumps because the temperature underground is consistent at between 9 and 12 degrees Celsius.

Air-to-Air Heat Pumps

Air-to-air heat pumps act like air conditioning units, except they provide cooling in the summer and heating in the winter.

They may not work so well in areas with very cold winters and may need new or extra ductwork installed. They don’t provide hot water and usually only heat small spaces, not your whole home.

What is a Gas Boiler

A gas boiler is the appliance that’s used to heat the water that provides heating and hot water in the home. The gas comes from the main supply, and when ignited, it heats up the heat exchanger.

The heat then goes into the cold-water pipe and makes the cold water hot. A pump takes the hot water to each radiator in your home, and finally, because by now the water temperature will have dropped, it returns to the boiler to start the process again.

The most common boiler in the UK is a combi boiler. It supplies instant hot water and heating without the need for a feed tank or hot water cylinder.

Regular and System boilers are used in larger households. A regular boiler needs a cold-water tank and a hot water cylinder. A System boiler will only need a hot water cylinder.

All gas boilers installed after 2005 will be condensing boilers. Condensing boilers capture the heat that normally escapes from the flue and recycle it to create more heat. It means new boilers are much more efficient.

Pros & Cons of a Gas Boiler

Pros:

✔ Works well with existing UK heating systems
✔ Condensing technology means better efficiency
✔ Lower upfront costs compared to heat pumps

Cons:

✖ Relies on fossil fuels
✖ Rising gas prices are affecting heating costs
✖ High carbon emissions
✖ The government plans to phase out new gas boilers by 2035

Heat Pumps vs Gas Boiler

Considerations	Heat Pumps	Gas Boilers
Purchase and Installation cost without Government Grant	Air Source - £4,000 - £13,250 Ground Source - £11,000 - £28,000 Air to Air - £2,400 - £8,000	£3,500 - £6,500
Running Costs	£1,360	£1,240
Efficiency	300% - 400%	New Boiler 90%+
Lifespan	15 - 25 Years	10 - 15 Years
Maintenance	Annual check recommended	Annual check recommended
Carbon Emissions	Low – 1,360kg CO2 Per Year	High – 1,240kg CO2 Per Year
Space Requirement	Outdoor wall space required for the Air source unit. Garden space required for Ground Source Unit	Small amount of wall space
Performance in Cold Weather	Not suitable for particularly cold locations	Works well in any weather
Suitability	Better in well-insulated homes	Works well in new and older homes
Government Incentives	Boiler Upgrade Scheme (BUS) for heat pumps	New boilers are due to be phased out in 2035

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Cost Comparison

The four main costs you want to consider when comparing a heat pump to a gas boiler are the following:

Supply Costs

The cost of a new gas boiler is between £700 and £3,000. A combi boiler is the most cost-effective option. The price will depend on the manufacturer, the type of boiler and its features.

Air source heat pumps cost between £4,000 and £13,250. Ground source heat pumps are between £11,000 and £28,000.

Air-to-Air heat pumps cost between £2,400 and £8,000.

Installation costs: It will cost between £3,500 and £6,500 to install an Air source heat pump. The cost will depend on the size of your property and the complexity of the installation.

Ground source heat pumps are much more expensive to install because of the excavation work that’s required. You can expect to pay between £10,000 and £25,000 for installation.

Air-to-air heat pumps are generally between £3,800 and £10,000 to install, depending on the size of your property.

Gas boiler installation costs are between £900 and £2,100. You’ll pay more if you have to have new pipework or flue work installed.

Running Cost

Heat pump running costs are difficult to assess because they depend on factors such as your home insulation, the efficiency of your heat pump, your heating demand and the electricity tariff you are using. However, on average, a heat pump costs about £1,360 per year.

A gas boiler is cheaper, but with gas prices rising, this might not be the case in the future. Currently, the average running costs of a gas boiler are £1,240 per year.

Maintenance Costs

Heat Pump Maintenance

Heat pumps are low-maintenance. Make sure the outdoor unit isn’t obstructed by falling leaves or branches, and have it serviced once a year to maintain its efficiency. The average price for a heat pump service is around £250, but if you live in London or the South East of England, you may pay more. A well-maintained heat pump should last between 15 and 25 years.

Boiler Maintenance

To keep your boiler well-maintained, it’s a good idea to have an annual maintenance check, which normally costs between £200 and £350. Suppose you have a problem with your system. Your engineer may recommend that you have a power flush. This drains your system and cleans it completely.

The cost of a power flush will depend on the number of radiators you have in your home, but average costs are between £450 and £800. A well-maintained boiler should last around 15 years.

Futureproofing

Heat pumps better align with long-term energy goals and future regulations.

Fine in the short term, but after 2025, a gas boiler can’t be replaced.

When you’re looking at a heat pump vs a boiler, the chart shows that while a gas boiler is cheaper upfront and compatible in most homes, heat pumps are future-proof, more efficient and environmentally friendly, although the upfront costs are higher.

In comparison to a boiler, a heat pump is more efficient. A boiler will convert 90% of fuel into heat that’s used. A heat pump produces 3 to 4 times as much heat for every unit of electricity; that’s 300 to 400%.

Efficiency and Performance: Heat Pumps vs Gas Boilers

Both heat pumps and gas boilers are efficient ways to have hot water and heating in the home. Heat pumps, however, tend to work better in milder climates. In places that have very cold conditions, heat pumps may need to be backed up with an additional form of heating.

Whereas boilers will provide heat and hot water even in very cold climates. So, in this case, if you’re living in an area that’s particularly cold and you’re looking at an air source heat pump vs a gas boiler, then you might be better off considering a ground source heat pump instead.

How efficient are heat pumps? Their efficiency is represented by the Coefficient of Performance measurement (COP), which measures the ratio of heat output to electricity output, as well as the Seasonal Performance Factor (SPF). A high COP and SPF reading means the heat pump is running efficiently. A good heat pump will generally have a COP and SPF of between 3.0 and 5.0.

A gas boiler’s energy efficiency is commonly expressed using A to G ratings. A is the best and G is the worst.

The ratings are:

A - The boiler has an efficiency of 90% or more
B - between 86% and 90%
C - between 82% and 86%
D - between 78% and 82%
E - between 74% and 78%
F - between 70% and 74%
G - is below 70%

Environmental Impact

The government plans to phase out new gas boilers in 2035 as part of the incentive to reduce our reliance on fossil fuels and meet its target of zero emissions by 2050.

Heat pumps aren’t carbon-free, but they do use significantly less CO2 per year than gas boilers. An air source heat pump produces, on average, 1,360kg of CO2 annually compared with a gas boiler, which produces around 1,240kg of CO2 each year.

Another advantage to heat pumps is that they can be combined with solar panels, which will reduce your energy bills even further. To encourage householders to go green and swap boilers for heat pumps, there are several government grants available.

If you want to swap a boiler for a heat pump, there’s the Boiler Upgrade Scheme (BUS), which offers up to £4,000 off the cost of a heat pump and hire purchase or leasing options to spread the upfront costs. Families living in deprived areas and with a gross annual income below £36,000 may also be eligible for a heat pump under the Warm Home Plan.

Practicalities

If you don’t have much space, your budget is tight, and you live in an older property, you may want to buy a new boiler and think about renewable options later.

Installing a heat pump is a big investment, even with the government’s grant. You’ll need to have space to put the outdoor unit for an air source heat pump or enough garden to lay pipes or sink boreholes for a ground source heat pump.

You may also need to spend extra money to upgrade your home insulation if you have an old home, or increase your electrical capacity or the size of your radiators.

Although the law has changed regarding where you can put the heat pump unit (previously it couldn’t be within one metre of your neighbour’s property), you still need to consider the noise the unit makes.

Most modern heat pumps are as quiet as a fridge, but this might seem loud at night when there’s no background noise.

The Future of Gas Boilers

As the government boiler phase-out gets closer, you’ll need to change the way heating and hot water are supplied to your home.

The government incentives will likely increase for heat pump adoption. We’ve already seen an increase in the budget for the Boiler Upgrade Scheme.

Future developments might include low-interest finance options to help bridge the gap between the government grant and the rest of the purchase and installation costs of a heat pump, which will make it more affordable.

A gas boiler needs less space and is cheaper to buy, but you can’t replace it once it reaches the end of its life. But if you want a short-term solution, then a gas boiler is a budget-friendly option for 10 to 15 years. If you have space and want to start going green and future-proof your home, now’s the time to think about a heat pump.