A practical guide to understanding when radiator upgrades are necessary.
One of the most common questions when considering a heat pump is whether the existing radiators will need to be replaced or upgraded. The answer is: it depends on your home and how well the current radiators perform at lower temperatures.
Heat pumps work best at lower water temperatures (typically 35–45°C), whereas traditional gas boilers often run at 60–80°C. This means radiators need to be larger to deliver the same amount of heat at these lower temperatures.
If your current radiators are too small, the heat pump may struggle to keep your home warm on colder days, or it will have to run at higher temperatures, reducing its efficiency.
If your current system struggles to maintain temperature when it’s cold outside, the radiators may be undersized for low-temperature operation.
Inconsistent heating often points to radiators that aren’t large enough to deliver adequate heat at lower flow temperatures.
This can indicate that the emitters (radiators) aren’t capable of delivering enough heat at the temperatures the heat pump is designed to run at.
If a proper heat loss calculation shows that your current radiators are undersized, this is usually reliable advice.
This is the most common solution. Larger radiators (or double-panel/double-convector types) can deliver enough heat at lower temperatures. This is often the most straightforward option in older properties.
In some rooms, adding an extra radiator can help deliver more heat without replacing existing ones. This can be a cost-effective middle ground.
Underfloor heating works very well with heat pumps because it operates at lower temperatures. This is often the best long-term solution in major renovations or new builds.
In well-insulated homes with reasonably sized radiators, it may be possible to keep the existing ones — especially if the heat pump is correctly sized and the home doesn’t have high heat loss. A proper heat loss calculation will confirm this.
Use our Heat Pump Estimator to get a better understanding of what your home would need.