Understanding the most important step in designing a heat pump system.
A heat loss calculation is the foundation of any successful heat pump installation. Without it, the system may be the wrong size, leading to poor performance, higher running costs, and disappointment.
A heat loss calculation works out how much heat your home loses on a cold day. It considers factors such as:
The result tells the installer what size heat pump you need and what size radiators or underfloor heating system is required to keep your home comfortable.
An undersized heat pump will struggle to keep your home warm on cold days. An oversized heat pump can be inefficient, more expensive upfront, and may short cycle (turn on and off frequently), which can reduce its lifespan.
A correctly sized and designed system runs more efficiently. This usually means lower electricity bills and better comfort. Skipping a proper heat loss calculation is one of the most common reasons for disappointing heat pump performance.
The calculation also determines what size emitters you need. Without it, you may end up with radiators that are too small to work effectively with a heat pump running at lower temperatures.
Replacing a heat pump because it was the wrong size from the start is expensive and disruptive. A proper heat loss calculation helps avoid this situation.
When speaking to installers, ask whether they will carry out a full room-by-room heat loss calculation. Be cautious of anyone who quotes based only on the size of your current boiler or a rough estimate of your floor area.
A good installer will usually:
Use our Heat Pump Estimator to get a realistic indication based on your property.