Here at Wunda group, we often get approached by customers who are weighing up whether to stick with their radiators when they install their heat pump, or if they should consider switching to a different heat emitter.
If you are considering a heat pump, one of the biggest questions is what type of heat emitter you should use. So we have put together this article to help guide people who are wondering on that very question.
The two most common options of heat emitters are radiators and underfloor heating.
Both can work with heat pumps, but they behave differently. The best choice depends on the property, the heating design, the heat loss of each room, and the flow temperature the system needs to keep the home comfortable.
Why heat emitters matter
Heat pumps work best when they can heat a home using low flow temperatures.
The heat emitter’s job is to transfer heat from the heating water into the room. If the emitter is too small, the system may need hotter water to deliver enough warmth. That makes the heat pump work harder and can reduce efficiency.
So the question is not simply: “Can this emitter heat the room?” The better question is: “Can this emitter heat the room at a low flow temperature?”
Standard radiators with heat pumps
Standard radiators can work with heat pumps in some homes.
However, many existing radiators were originally sized for boiler systems to work with high temperature water (60-80°C). So the radiators may not have been designed to deliver enough heat at lower heat pump friendly flow temperatures (Lower than 55°C).
If the radiators are too small, the heat pump may need to increase its flow temperature to keep the room warm. That can reduce efficiency.
Standard radiators are most suitable when:
- the home has low heat loss;
- the radiators are already large enough;
- the system has been checked for low-temperature operation;
- the heat pump can run steadily without needing high flow temperatures.
In some retrofit projects, standard radiators may be fine. In others, they may need upgrading.
Oversized, low temperature radiators with heat pumps
Oversized radiators are a common solution for heat pump systems. By increasing the radiator surface area, the room can receive enough heat at a lower water temperature. This makes the system more compatible with heat pump operation.
Oversized radiators can be a practical option where homeowners do not want underfloor heating installed. They are easy to install and they can improve low-temperature performance while using a familiar radiator-based system.
The main drawback is that larger radiators take up more wall space. They may affect furniture placement or room layout, especially in smaller rooms.
So oversized radiators can be useful, but they are still a compromise compared with using the whole floor as the heat emitter.
Screed underfloor heating with heat pumps
Underfloor heating works well with heat pumps because it uses a large surface area to heat the room.
Instead of relying on smaller wall-mounted emitters, the whole floor becomes the heat emitter. This means the system can often provide comfort using lower water temperatures.
Traditional screed underfloor heating can therefore be efficient with heat pumps. The main drawback is it’s response time.
Screed has high thermal mass. The pipes heat the screed first, and the screed then slowly releases heat into the room. Once warm, it can provide steady comfort, but it may take hours to heat up or cool down.
This can make it less practical for home life being less flexible for homes where rooms are used at different times of day.
For example, a bathroom may only need warmth before a shower. A home office may only need heating during working hours. A spare room may only need occasional heat.
With a slow screed system, this kind of responsive room-by-room control is harder to manage.
Overlay underfloor heating with heat pumps
Overlay underfloor heating is designed to sit above the existing floor structure rather than being buried in a thick screed slab.
Low thermal mass overlay systems, such as Wunda Rapid Response®, are designed to transfer heat into the room more quickly. Instead of heating a heavy slab first, they reduce the amount of material that needs to warm up before the room feels comfortable.
This gives overlay underfloor heating two key advantages with heat pumps.
First, it supports low flow temperatures, helping the heat pump run efficiently.
Second, it responds more quickly than traditional screed underfloor heating, making zoning and smart scheduling more practical.
This means different rooms can be heated according to how they are actually used, rather than keeping the whole home at one temperature all day.
Comfort differences
Radiators heat from specific points in the room. This can create warmer and cooler areas, depending on layout, radiator position and room design.
Underfloor heating spreads heat more evenly across the floor area. This can create a more balanced feeling of warmth, especially when designed and controlled properly.
Zoning also becomes important. Different rooms need different temperatures. Living rooms, bedrooms, bathrooms and home offices all have different comfort requirements.
Which is better for a heat pump?
For many homes, the best option is the one that allows the heat pump to run steadily at the lowest practical flow temperature while still giving the homeowner good comfort and control.
Radiators can work with heat pumps if they are correctly sized for low-temperature heating. Oversized radiators can be a practical retrofit solution.
Screed underfloor heating offers low-temperature performance but can be slow to respond.
If overlay underfloor heating systems can be accommodate, they offer the most benefits with low-temperature performance with faster response and better room-by-room flexibility.
Final conclusion
Both radiators and underfloor heating can work with heat pumps.
The key difference is how easily they can heat the home using low flow temperatures.
Standard radiators may need checking or upgrading. Oversized radiators can help. Screed underfloor heating can be efficient but slow. Overlay underfloor heating such as a Rapid Response® Wundafloor combines low-temperature operation with faster response and better zoning potential, leading to more comfort and efficient control.
The best heat emitter is not just the one that gets warm. It is the one that helps the heat pump run efficiently while keeping each room comfortable.