Replacing a gas boiler with a heat pump can reduce your home’s carbon emissions and even reduce the cost of your energy bill in the right circumstances. This is because heat pumps are extremely efficient at generating heat.

Heat pumps generate around 3kWh of heat for every 1kWh of energy used, while gas boilers generate around 0.93kWh of heat per 1kWh of energy used.

And while the number of heat pumps installed in the UK lags far behind many European countries, there’s never been a better time to buy one thanks to falling costs and rising grant scheme payouts.

But before you go ahead and buy a heat pump, there are a few things you should consider first...

1. What type of home do you have?

The type of home you have will impact the type of heat pump you could install and its effectiveness.

Flats

Flats don't usually have the necessary space to install a heat pump. But if there is space, it may be possible to install a heat pump for an individual flat or to install several heat pumps to be shared by all flats within the building (as was recently done for 270 flats in Thurrock).

Modern and well-insulated houses

A heat pump could be a viable option if you’ve got a modern, well-insulated home. This is because heat pumps operate at low temperatures and require suitable insulation and heating systems to deliver efficient heating.

Well-insulated homes are also likely to be eligible to receive funding towards the installation via the Boiler Upgrade Scheme, since they’ll probably already have loft and cavity wall insulation.

Older and draftier houses

If your home is older and draftier, you may need to prepare it before considering a heat pump. If heat is easily lost, a heat pump will struggle to heat your home efficiently. So you’ll want to address its energy efficiency before getting a heat pump.

If you don’t already have suitable loft or cavity insulation, you’ll be less likely to be eligible to receive funding support via the Boiler Upgrade Scheme.

Houses with limited outdoor space

The amount of outdoor space you have could also impact the type of pump you’re able to install. Ground source heat pumps require at least a small patch of land to drill vertical piping deep into the ground(larger gardens will allow shallow piping to be laid horizontally).

If you have a larger garden, a horizontal ground loop system would likely be most suitable. It involves laying pipes horizontally in shallow trenches, the length of which will depend on the space available and your heating requirements.

If you have a smaller garden, a vertical borehole system could be more suitable. This involves driving pipes 75-200 metres into the ground, which can be more costly than horizontal systems but requires far less space.

Air source heat pumps (ASHP) only need space for the unit itself, so are most suitable for houses with limited outdoor space.

2. Is your home well insulated?

Insulation plays a huge role in how efficiently a heat pump will work in your home. While you could, in theory, get a heat pump regardless of your home’s level of insulation, you might want to wait while you improve your home’s insulation first.

Heat pumps use energy to generate heat (approximately 1kWh of energy per 3kWh of heat), so a well-insulated home can be a very efficient one.

But if your home’s not well insulated, the heat pump will have to work harder. It’ll use more energy to generate more heat, and the heat it does generate will have to be replaced much sooner. It’ll also be less likely to meet the criteria required to receive funding support via the Boiler Upgrade Scheme.

3. How large is your home?

Heat pumps come in various sizes, from 4kWh to 16kWh and beyond. So you’ll need to find one that matches the requirements of your home (the more insulated the home, the smaller the heat pump required).

The general rule of thumb is that the average home needs 5kWh per 100m². So a typical three-bedroom home might need a 6kWh heat pump.

However, an installer can assess your home to identify the exact size of heat pump you need.

4. What heating system does your home currently use?

Each type of heat pump will integrate with your heating system in a different way. So, depending on whether you’re willing to have extra work done, this could influence the type of heat pump you choose.

Here’s what each type of heat pump requires:

• Ground source heat pumps work best when paired with underfloor heating systems. This is because underfloor systems operate at lower temperatures than radiators. This compliments ground source heat pumps which are most efficient when producing lower temperatures.
• Air-to-air heat pumps work by circulating warm air throughout the home using a fan and vent system. So, you won’t be able to use an air-to-air heat pump with your existing radiators.
• Air-to-water heat pumps also work best with underfloor heating systems. They can also work with radiators, but they’ll need to be larger units with a larger surface area to work well at lower temperatures (most traditional radiators are smaller and won’t be as effective).

If you want to rely solely on the heat pump to generate all your home’s heat, you can free up some space by removing your existing boiler. Or if your boiler’s compatible, you could also keep it and pair it with a new hybrid heat pump. 

5. Consider the right type of heat pump for your needs

There are three main types of heat pumps to choose from, each with its advantages and considerations:

• Ground source heat pumps absorb heat from the ground using underground pipes. They’re incredibly efficient but have a higher up-front cost due to the need for underground piping.
• Air-to-air heat pumps capture outdoor air heat and distribute it indoors using fans. They’re generally more affordable and easier to install but are not as efficient in very cold weather.
• Air-to-water heat pumps capture outdoor air heat and transfer it to a water-based heating system. They’re versatile, providing both space heating and hot tap water, but their efficiency is average compared to other pump types.

There are also hybrid heat pumps which combine a ground or air source heat pump with a traditional gas boiler, switching between the two depending on weather conditions.

When deciding the type of heat pump that’s right for your home, you’ll want to think about your budget, the outdoor space you have available and how compatible each type is with your current heating system.

6. Estimate costs and savings

As well as being better for the environment, a heat pump could be good for your wallet too. But while costs have come down in recent years, they’re still one of the most expensive efficiency improvements you can buy.

You’ll want to consider:

• The upfront cost starts from around £8,000 depending on the size and brand of the unit. Bear in mind that grants can reduce this cost (we’ll cover this in the next section).
• Running costs will vary depending on the size of the unit, the efficiency of the unit, the size of your home and how well-insulated your home is.
• Potential savings will vary depending on your current heating system, your typical energy usage and the type of heat pump you’re replacing it with (which may require the upgrading of your hot water tank, piping and/or radiators - costing an average of £3,000).

Calculating all this can be tricky. But you can make the task simpler by using our energy efficiency planner. This will calculate the estimated upfront cost, any grants that might be available, the estimated installation cost and ongoing costs and savings. It’ll also calculate the payback time which shows how long it’ll take for the savings to surpass your original upfront investment.

7. Check for grants

To encourage the take-up of heat pumps in favour of environmentally damaging gas and oil-burning heating systems, the government has announced several grant schemes to support homeowners with the cost.

If you qualify for one of the schemes, you could receive a free contribution towards part or all the cost of the heat pump.

You can learn more about grants by reading our grants guide, and you can check your eligibility by using our energy efficiency planner.

8. Check if you need to apply to your local planning authority

In most cases, you won’t need to apply for planning permission to install a ground or water-source heat pump. But if you live in a listed building or conservation area, it’s a good idea to check with your local council for any extra rules.

If you’re not sure, speak with an installer who should be on top of the relevant planning rules.

9. Inform your local District Network Operator

Before you have a heat pump installed, you’ll need to get approval from your District Network Operator (DNO).

A DNO is responsible for managing the physical infrastructure that delivers electricity to your home.

Fortunately, you shouldn’t have to complete the application yourself as this is something your installer should do on your behalf. But given the process can take up to three months, you’ll want to think about this long before you plan to get the heat pump installed.

10. Find a qualified local installer

Installing a heat pump is a complex and potentially dangerous job, so it’s not something you can do yourself. Instead, you’ll need to hire a qualified installer who’s accredited by a reputable scheme, such as the Microgeneration Certification Scheme (MCS). This will ensure the heat pump is installed to the highest standards.

You can find a qualified local installer by searching online tradespeople directories, asking friends for recommendations, or using the MCS installer directory.

Another easy way to find an installer is to use our energy efficiency planner. We’ve partnered with EDF and Heat Save Scotland to source qualified and vetted installers in every region of the UK. We recommend getting three quotes from different installers for a fair comparison.

11. Ready your home for the installation

Depending on the type of heat pump you’re having installed, the severity of disruption will vary:

• Air heat pumps will be least disruptive since they are usually installed on the side of your building. But you’ll still need to clear all access areas and be on hand to deal with any questions the installer may have about your home. You may also need to replace radiators, piping and/or a hot water tank, which the installer can do at the same time to minimise disruption.
• Ground heat pumps can be quite disruptive since large excavators will need to dig long lanes across the garden or drive pipes deep into the ground. This may require reserving road space overnight for the machinery to park during the day, and you may want to give your neighbours a heads-up!

For more information about heat pumps, read our heat pump guide.