Can you Use a Heat Pump with an Existing Combination Boiler?
If you’re looking to reduce your energy bills, use more sustainable heating methods and find a reliable way to heat your home, then a hybrid heating system may be the perfect solution.

Key Points:
What are heat pumps?
Heat pumps are a type of a heating and cooling system that uses environmentally conscious energy to generate heating and hot water to your home. They work by extracting thermal energy from the ground, air or a local water supply. The heat pump then converts this thermal energy into heating and hot water.
Heat pumps operate by collecting heat through an external collection system, which are pipes containing liquid filled with antifreeze to transfer the heat from ambient temperature.
Can you have a heat pump and a combi boiler?
Yes, you can have a heat pump and a combi boiler, using what is known as a hybrid heat pump. The boiler is used to ‘top-up’ a low temperature heat pump in order to meet the demands of a property in which a heat pump cannot do it alone. It also continues to provide hot water.
Heat pumps usually work at lower temperatures than boilers. Without the correct insulation in our homes, or upsizing radiators, low temperature heat pumps aren’t suitable for existing properties. If the heat pumps are fitted incorrectly, there are risks that homes may fail to heat or there may be a huge increase in electricity bills.
Hybrid heat pumps let the heat pump run at an efficient temperature of around 40C, which will provide sufficient heat for a large part of the year. As the outside temperatures drop, and when the hot water is used, the boiler can step in.
Plan your Hybrid Heating System
How do heat pumps work with radiators?
A big question that many people have when considering having heat pumps is if they’ll work with existing radiators. Often, the answer to this question is ‘it depends’.
The temperature of the water flowing around your central heating system needs to be higher when using a gas boiler than it does in an air source heat pump. This will either be expressed as ‘high flow temperature’ vs ‘low flow temperature’ and is one of the big reasons that heat pumps are more efficient than boilers.
The existing radiators in your home will have been installed to ensure that their heat outputs are large enough to heat your room when the flow temperature from your boiler is high. However, when you use a heat pump, the flow temperature is much lower, so you would need to ensure that your radiators are still able to heat your room effectively.
In some cases, you may need to upgrade your radiators to a larger size to ensure they have enough surface area to emit enough heat in order to comfortably warm the room.
However, in recent years it has become common practice for heating installers to install ‘oversized’ radiators. This is to ensure that the radiators are actually capable of heating a much larger space and would therefore be suitable for heating a room even if they operated at a lower flow temperature.
If your radiators are ‘oversized’, then it is very likely you won’t need to change them when you get a heat pump. The best way to find out is to speak to our professional heating system installers at Lacey Plumbing & Heating to get a definitive answer.

Can you install a heat pump onto a system which already has a combi boiler?
Yes, you can add a heat pump to a combi boiler system, but there are a few things you should consider before doing so.
Determine your current boilers setup
You’ll first need to determine the existing setup of your boiler before you buy a heat pump. This will help you establish the heat pumps size, type and location.
Consider your homes heating needs
When you’re replacing your heat source with a heat pump or adding in a heat pump, consider the current heating needs of your home. It is better to have a full professional survey before you can consider installing a heat pump.
Calculate the costs of the heat pump
To calculate how much a heat pump will cost, you should first determine how much your current boiler costs to run. You can do this by asking your energy provider. The next step is to consider the energy savings you could benefit from with a heat pump instead of a traditional boiler.
Once you’ve established what the difference is between the two, you can then proceed with either sticking with your current heating system or upgrading to a heat pump.
Are there benefits to keeping your combi boiler and having a heat pump?
There are a number of benefits of having a hybrid heating system, including:
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