Whether it’s for cooling or heating, a heat pump will make your home comfortable and increase its energy efficiency. But for your heat pump to work optimally and save you money, it has to have the right amount of power.
How big or small is the heat pump I need?
Generally, the bigger the house the bigger the heat pump. Depending on heat loss, property age, and room types, a 100 sq m house may need a 7kW air source heat pump. This doubles to 8kW or 10kW respectively for 200 sq m houses.
However, these figures must be taken with a pinch of salt. It is not a guaranteed equation, because there are many things that could affect the calculation.
Type of property
The size of heat pump for new build houses is easy to calculate, because in order to comply with building regulations in the UK, properties must have certain levels of insulation. The heat loss level is calculated accurately at the design stage, and therefore the size of the heat pump is relatively easy to predict.
Calculating heat loss in older properties is more challenging, and for houses built before the turn of the century a detailed survey of the building is always required before a heat loss assessment can be undertaken.
Important questions need to be answered about:
- Insulation, property fabric, and heat loss
- Size of radiators and/or underfloor heating
- The number of rooms in the property
- The types of rooms and their uses
- The desired indoor temperature for different rooms
- Seasonal temperature fluctuations
The number of different types of room is a consideration, because some rooms need to be heated more intensively than others; for example, living rooms generally need to be kept warmer than bedrooms, and bathrooms warmer still. So the number and type of rooms add up to determine the overall heat demand of the house and therefore the size of the heat pump.
For homes in the UK, they often install heat pumps which are 4kW, 5kW, 6kW, 8kW, 10kW, or 12kW sizes. We can go bigger, of course. But this is only really needed for very large properties, shared heat pump systems, and district heating installations.
The heating system you are using
Heat pump sizing will need to account for the type of heat distribution system you plan to use. Underfloor heating, for example, can run at a much lower flow temperature, whereas radiators need higher temperatures and larger surface areas to maintain a comfortable heat level in the home. Correct sizing of radiators, as well as your desired temperature for that room, will all affect the size of heat pump you’ll be recommended.
To be confident you are getting the right sized heat pump for your home, you must ensure your installer is MCS certified. This is also essential for eligibility to the RHI. You should also look for installers who are members of either the Home Insulation and Energy System Contractors Scheme (HIES) or the Renewable Energy Consumer Code (RECC), as this will give you peace of mind that their customer care is up to scratch.
The available sizes of heat pumps from Zealux
Zealux air to water heat pumps come in sizes ranging from around 7kW up to 27kW, with the higher rated pumps producing more heat for your home. A heat pump which is correctly sized should be able to adequately heat your home all year round, but that doesn’t mean that bigger is better. If it’s too big, it will short cycle, meaning it shuts off too soon before coming back on for another brief period, which is not an efficient way to run.