Article by Tim Beecher, Retrofit Assessor, Domestic Energy Assessor
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If you’re considering switching to an air source heat pump (ASHP), you’re already on the path to a more sustainable and energy-efficient heating system. But while the heat pump itself is key, how that heat is delivered throughout your home is just as important. Unlike traditional boilers, a heat pump doesn’t generate high-temperature heat quickly—it works best when it distributes stable, consistent warmth across a large area. So, what’s the best way to deliver that heat efficiently?
Let’s explore the three main heat delivery systems commonly paired with heat pumps—wet underfloor heating, wet central heating with radiators, and electric radiators—to help you decide which is right for your home.
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1. Underfloor heating: The gold standard for heating efficiency
A wet underfloor heating system is widely considered the most efficient companion for an air source heat pump. Why? It all comes down to temperature and surface area.
Underfloor heating operates at much lower temperatures than conventional radiators—typically between 30–40°C (compared to 55-60°C for gas powered radiators). This makes it a perfect match for heat pumps, which perform most efficiently when providing low-temperature heat. Because the entire floor acts as a large heat emitter, it distributes warmth evenly and comfortably throughout the room. In addition to the heat delivery system itself, you will also need to install a hot water cylinder.
Pros:
- Maximises heat pump efficiency
- Comfortable, even heat distribution
- No bulky radiators on walls
- Ideal for new builds or full renovations
Considerations:
- Higher upfront installation cost
- Most practical in homes undergoing flooring upgrades or renovations
2. Wet central heating: A direct replacement option for a combi-boiler
If your home already has a wet central heating system (i.e., one that uses water-filled radiators), you can usually replace your existing combi boiler with an air source heat pump. This is a practical option for many homes, especially where major structural changes aren’t feasible.
However, because heat pumps operate at lower temperatures than gas boilers (should be a design flow temp of 45 to 50oC (max) with radiators and an ASHP), your radiators may need to be upsized to maintain comfort levels. Additionally, since combi boilers heat water on demand, you’ll need to install a hot water cylinder with your heat pump to store and deliver hot water.
Pros:
- Makes use of existing radiator infrastructure
- Easier retrofit than underfloor heating
- Suitable for a wide range of property types
Considerations:
- May require radiator upgrades
- Requires space for a hot water cylinder
- Slightly less efficient than underfloor heating
3. Electric convection heaters: A smarter use of electricity
Homes currently using electric convection radiators can also benefit from heat pump technology. Compared to plugging convection heaters straight into the mains, using an air-to-air heat pump is significantly more efficient. Thanks to the Coefficient of Performance (CoP) of heat pumps, you can get up to 4 kWh of heat for every 1 kWh of electricity used. That’s 400% efficient compared to the 100% efficiency of a direct electric radiator.
They supply direct warm air into a room, like an air-conditioning unit operating in reverse. In fact, they can also act as air conditioning/ cooling devices in the Summer. However, these heating systems do not supply hot water, so homeowners would need a hot water electric immersion tank or single point water heater under a sink to provide this.
Pros:
- Huge energy savings over direct electric heating
- Lower running costs
- Improved carbon footprint
Considerations:
- May require significant rewiring or plumbing changes
- Not always straightforward to retrofit into existing electric-only systems
Which heating system is best for your property?
If you’re building a new home or undertaking major renovations, underfloor heating is the best heat delivery system to pair with a heat pump, thanks to its low temperature requirements and superior efficiency.
For existing homes with wet radiator systems, retrofitting your setup with an air source heat pump can still be a smart and efficient choice—just make sure to consider radiator sizing and hot water storage.
And for homes with electric heating, moving to a heat pump-supported system is a huge step up in both energy efficiency and cost-effectiveness.
Whichever path you choose, optimising your heat delivery system is key to unlocking the full potential of your heat pump investment.
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Need help deciding what’s right for your property? A BHESCo Energy Survey will provide the data and insights you need to make the right decisions and achieve the best outcomes.
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