Retrofitting Existing Heating Systems with Air Source Heat Pumps

Author : Andrew Garfield | Published On : 29 Apr 2024

Want to save money on energy bills and help the environment? Air source heat pumps (ASHPs) might be perfect! They're popular because they save energy and money. But what if you already have a boiler? Can you add an ASHP to your setup? We’ll address this question later in this article. In addition, you can get a free air source heat pump. The UK government offers grants to replace outdated heating systems. Interested in details? Visit this page:  With or without the government's help, getting an air source heat pump is an amazing investment for the pocket and the environment. 

Air Source Heat Pumps

What’s an air source heat pump?

An air source heat pump is a type of heater. It uses electricity and renewable energy. But instead of burning fuel like gas or oil, it takes heat from the air outside. Then, it uses it to warm your home. Moreover, they're super efficient and save you money.

Though these pumps are not very common in UK homes, unlike in countries like Norway, gradually they’re becoming popular.  In the UK, less than 2% of homes have them, while in Norway, more than a third of homes do!

Why aren't heat pumps as popular in the UK? Well, mainly because people don't know much about them. They're used to using boilers. But, installing heat pumps is easy, and they save a lot of money. So, now's a great time to get one!

Retrofitting air source heat pump

Retrofitting an air Source heat pump (ASHP) is the process of installing a new ASHP system in

place of your existing heating system, like a boiler. It's like giving your

home's heating an upgrade!  "Retrofit" means modifying an existing system. So, an ASHP retrofit involves replacing your old boiler with an air source heat pump. Consequently, this breathes new life into your heating system. Moreover, it makes your place more efficient and environmentally friendly.

What are the benefits of a retrofit?

  • Energy savings: ASHPs are much more efficient than boilers, using less electricity to generate heat. This translates to lower energy bills.

  • Eco-Friendly: They rely on renewable energy from the air, reducing your carbon footprint compared to burning fossil fuels.

  •  Potential for cooling: Some ASHPs are reversible, providing cool air during hot summer days.

Why call it a retrofit?

Because you're not installing a completely new heating system. You're keeping most of your existing infrastructure (pipes, radiators) and replacing the boiler with a more modern and efficient technology - the air source heat pump.

Can air source heat pumps work with existing radiators?

Yes, they can! You can use an ASHP with your current radiators with just a few changes.

First, understand how your system works. You likely have radiators or underfloor heating powered by a gas or oil boiler. Some radiators might need upgrading or be made bigger to work with the lower temperatures of an ASHP.

After preparing your system, you install the ASHP. It connects to your existing radiators and convectors, so they get warm air from outside.

Costs of installing retrofit air source heat pump

Costs for installing an ASHP in your existing radiator system vary. Factors like house size and number of radiators affect it. Usually, it's around £12-14k.

But, there are savings:

  • No VAT until 2027

  • Government grants up to £5,000

  • £2000 funding from some banks like Barclays

ASHPs are popular because they're efficient and save money. If you have an existing system, you can switch to green tech without changing everything. This saves time, money, and cuts down greenhouse gas emissions from your home.

Is my home suitable for an ASHP retrofit? 

Most UK homes are suitable for ASHP retrofits. Here are some things to consider:·        

Property Size: ASHPs work best in well-insulated homes. If your home has poor insulation, consider upgrading your windows and doors before installing an ASHP.   

Radiator System: Your existing radiators might need to be adjusted to work efficiently with an ASHP. They typically operate at lower water temperatures than traditional boilers.


Hot Water Needs:

Consider your hot water usage. Some ASHPs might need a larger hot water cylinder to meet your needs.

Retrofit process: Step-by-Step

Here's a simplified overview of the ASHP retrofit process:

  • Get a Quote: Contact qualified ASHP installers and get quotes. They'll assess your home and recommend the best system for your needs.

  • Check Eligibility: Research government grants and check if you qualify for financial assistance.

  • Schedule Installation: Once you've chosen an installer and secured funding, schedule the installation date.

  • Installation Day: The installers will remove your old boiler and install the ASHP unit outside your home. They might also need to adjust your existing pipework and radiators.

  • System Check: After installation, the engineers will check the system thoroughly to ensure it's functioning correctly.


Retrofitting your existing heating system with an ASHP is a fantastic way to improve energy efficiency. It reduces your carbon footprint. As a result, you can enjoy a more comfortable home. Moreover, with free air source heat pump grant, you may get totally free installation.