Heat pumps do work with radiators, but integrating a new heat pump with your existing radiators can be difficult. This is because they both work most effectively at different temperatures. A regular radiator is built to work with a high-temperature heating system, such as your gas boiler, whereas a heat pump operates at lower flow temperatures for optimal efficiency. As a result, not all radiator and heat pump combinations will provide the heat and efficiency you require.
In this blog, we explore how heat pumps and radiators work together, how to address challenges you may face, and how to get the most efficient delivery of heat throughout your home.
Heat pumps warm your radiators using water at much lower temperatures than a gas boiler. Where a conventional boiler may run at 60-80°C, a heat pump is much closer to the 35-55°C mark.
This temperature is known as the “flow temperature”: the temperature at which hot water leaves the heat source and goes into your radiators. In the case of heat pumps, this lower flow temperature makes them much more efficient than a gas boiler, as instead of burning fuel to produce heat, it gently moves heat from outside into your home and keeps it there.
A potential issue is that your radiator now has to work harder with less. At a lower flow temperature, the radiator needs to be a suitable size to release the same amount of heat into the room.
In some cases, you can keep your existing radiators and have the heat pump warm them up, but in certain cases, you may need an upgrade. It ultimately comes down to size, insulation, radiator age, and performance of the existing system.
You can combine a heat pump with a radiator, but only in some cases:
In some cases, your radiators may not be suitable for combining with a heat pump. Examples include:
In simple terms, large radiators work best with heat pumps. The more panels and fins it has, the more surface area there is for heat exchange. This means you’ll get more heat at a lower flow temperature.
A range of radiator sizes are found in homes across Sussex. These include:
Radiators for heat pump systems need to be roughly 2.5x the surface area of a radiator that typically runs off a boiler system, so bear this in mind when you decide to upgrade.
| Radiator type | How it works with a heat pump | Verdict |
| Steel panel | The most common type. Works well at low flow temperature, if sized large enough. Cost-effective to retain or upgrade | Good if correctly sized |
| Aluminium | Very high conductivity, heats & cools quickly, uses less water and reaches temperature faster | Best fit, but does cost more |
| Cast iron | High thermal mass, slow to heat and cool, designed for high-temperature systems | Poorest fit |
Before upgrading your radiators or adding a heat pump, it is worth having a heat loss assessment conducted.
A heat loss assessment from a qualified installer, conducted in each room, determines the home’s heat demand, which sizes both the radiators and heat pump.
If the heat pump is undersized relative to the heat loss of the home, you’ll see bills and discomfort increase.
If the heat pump is too big, efficiency drops and you’ll be spending money unnecessarily.
It is similar with your radiators; if the radiator is too small for the required flow temperature and heat demand, rooms may take much longer to warm up, and in some cases, might not reach the temperature you are aiming for.
The core reasons many people choose heat pumps are increased energy efficiency and lower bills. Optimising your radiators to get the best from them ensures your heat pump runs at its most efficient. Consider the following:
An air source heat pump will work with existing radiators in an old home, provided the current radiators have a large surface area and the property is sufficiently insulated. In some older homes where a heat loss assessment determines high heat loss, perhaps through poor insulation, draughts or solid walls, it may be best to install larger radiators or consider adding extra ones to cope with the heat demand.
A heat pump and radiator combination can be a great way to deliver warmth, efficiency and money-saving, but it may not always be the most suitable solution, especially if you need to overhaul your current radiator system for it to be beneficial. Our table below demonstrates some of the benefits and disadvantages of using radiators and heat pumps together.
| Advantages | Disadvantages |
| Reduced energy bills | Upfront costs may be high |
| Consistent warm temperatures | Space & aesthetics may be compromised |
| Compatible with many existing radiator systems | Potential retrofitting challenges |
| Reduced carbon footprint | Requires professional expertise and often, complex system design |
If you are considering heat pump installation in Sussex, speak to our team. At Sussex Air Conditioning & Heat Pumps Ltd, we install air-to-water heat pumps that feed your existing radiators and hot water cylinders, as well as air-to-air heat pumps suitable for domestic and commercial properties. With our MCS-accredited engineers, your installation may also qualify for the heat pump grant currently available from the government. To find out more about incorporating heat pumps into your property and connecting them to your radiators, contact us today.
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