Retrofitting an Air Source Heat Pump System

Last Updated on July 1, 2025

Considering retrofitting an air source heat pump system in your UK property? Whether you’re a homeowner looking to cut down on energy bills or a landlord aiming to improve EPC ratings and attract eco-conscious tenants, retrofitting an air source heat pump can be a game-changing move. 

In this guide, we’ll explore everything you need to know, from costs, challenges, benefits, and compatibility, so you can make an informed decision.

Can You Retrofit an Air Source Heat Pump in an Existing Property?

Yes, retrofitting an air source heat pump system into an existing home or rental property is possible in most cases. The key factor is whether your property is energy-efficient enough to make the system cost-effective. 

Retrofitting requires careful planning to ensure compatibility with your insulation, existing radiators, and overall heating demand.

Retrofitting is particularly popular in off-gas areas and older properties looking to move away from oil or LPG heating. For landlords, it’s also a strategic upgrade to meet Minimum Energy Efficiency Standards (MEES) and stay ahead of tightening EPC requirements.

What Are the Main Considerations When Retrofitting a Heat Pump?

When retrofitting an air source heat pump, several critical elements must be evaluated:

• Insulation quality (walls, roof, floors)
  
• Window glazing
  
• Existing heating system
  
• Flow temperatures
  
• Radiator and underfloor heating compatibility
  
• Outdoor space for the heat pump unit

In the UK, older homes often suffer from poor insulation, which can impact the efficiency of a retrofit. Before installation, a heat loss survey is recommended to identify areas needing improvement. Upgrading insulation often goes hand-in-hand with a successful retrofit.

Do You Need to Replace Your Radiators When Installing a Heat Pump?

Not always, but in many retrofitting scenarios, radiators must be upsized to accommodate the lower flow temperatures used by air source heat pumps (typically 35–45°C versus 65–75°C for gas boilers). Larger surface area equals more effective heat transfer.

Alternatives include switching to underfloor heating, especially in new extensions or ground floors. However, if you already have well-sized radiators and good insulation, replacements may not be necessary.

Will a Heat Pump Work with Your Existing Boiler?

Air source heat pumps can work in a hybrid system, operating alongside an existing boiler. This is especially useful in retrofit scenarios where complete replacement isn’t feasible right away. 

The hybrid setup ensures reliable heating during extreme cold while still reducing carbon footprint and running costs.

This approach is ideal for large homes or rural properties where demand may exceed what a standalone heat pump can deliver.

How Much Does It Cost to Retrofit an Air Source Heat Pump System?

The average cost to retrofit an air source heat pump system in the UK ranges from £7,000 to £14,000, depending on:

• Property size
  
• Insulation quality
  
• Radiator upgrades
  
• Hot water cylinder requirements

However, UK residents can reduce upfront costs via the Boiler Upgrade Scheme (BUS), which provides £7,500 grants for eligible air source heat pump installations.

For landlords retrofitting multiple properties, long-term savings and increased EPC ratings often outweigh initial investment.

What Are the Benefits of Retrofitting a Heat Pump System?

✔️ Lower energy bills (especially for properties off the gas grid)
✔️ Reduced carbon emissions
✔️ Improved EPC rating
✔️ Future-proof heating solution
✔️ Access to government funding

Air source heat pumps can cut heating-related emissions by up to 65%, aligning with the UK’s push toward net-zero 2050. For landlords, retrofitting supports compliance with potential EPC regulation changes requiring a minimum C rating.

Is Planning Permission Required to Retrofit a Heat Pump?

In most cases, planning permission is not required, especially if the unit is below 0.6m³ and meets permitted development conditions. 

However, listed buildings and conservation areas may require additional approvals. Always consult your local authority before installation.

A qualified MCS-certified installer will ensure your installation complies with Part L of the Building Regulations.

How Long Does a Retrofit Installation Take?

Most retrofitting jobs take 3 to 5 days, depending on the complexity. Timeframes vary if your home needs extra insulation work or significant radiator replacements. Pre-installation assessments (e.g. EPC, heat loss survey) should be factored in.

Professional installers will handle all paperwork, design calculations, and liaise with Ofgem for BUS grant applications.

Will Retrofitting a Heat Pump Add Value to Your Property?

Yes, retrofitting an air source heat pump is likely to increase property value. Buyers and tenants are increasingly prioritising energy efficiency and lower bills. A recent survey by Rightmove found energy-efficient homes can command up to 10% higher asking prices.

With energy prices expected to remain high, retrofitting isn’t just good for the environment, it’s a solid financial investment.

How Can You Make Sure Your Retrofit Is Successful?

1. Book a home energy assessment
   
2. Improve insulation where needed
   
3. Choose an MCS-accredited installer
   
4. Apply for the Boiler Upgrade Scheme
   
5. Opt for a smart control system
   
6. Schedule regular maintenance

Working with experienced, heat-pump-specific professionals ensures your system is correctly sized and commissioned.

Ready to Retrofit? Request a Free Air Source Heat Pump Quote from Eco Happy

Upgrading your home or rental property with a heat pump doesn’t have to be complicated, or costly. At Eco Happy, we specialise in tailored retrofit heat pump solutions for UK homes.

Whether you’re a homeowner trying to future-proof your energy or a landlord aiming to boost your EPC rating, our team handles everything, from surveys and quotes to grant applications and full installation.

MCS-Certified Installers
Full Boiler Upgrade Scheme Grant Support
Fast Turnaround with Expert Design & Advice

Don’t delay—start saving today.