Heat pump sizing: What size heat pump do I need?

A heat pump is a brilliant way to reduce your carbon footprint and increase your home’s energy efficiency. Not only are heat pumps low maintenance and have a long service life, but they are also a sustainable and emission free way of heating and providing hot water to your home.

When asking, ‘What size heat pump do I need?’ you are referring to its power output, measured in kilowatts (kW). This indicates how much energy the heat pump can generate for your home.

The size of the heat pump directly impacts its initial cost to purchase and install. Higher power output means a higher cost for both the appliance and its installation.

If you're wondering about the physical size of a heat pump, you’re asking about its dimensions. Heat pumps, particularly air source heat pumps, are generally compact units, about the size of two domestic wheelie bins, so they won’t take up too much space.

However, you still need to ensure you have enough room for correct installation and airflow.

The size of a heat pump can vary by manufacturer. Below is a breakdown of Vaillant heat pump sizing:

Heat pumps are rated based on their heating and cooling capacities, typically measured in British Thermal Units per hour or tonnes. One tonne is equivalent to 12,000 BTUs per hour. The size of the heat pump you need depends on various factors, including the size of your home, the local climate, insulation levels, and the number of windows and doors.

Your installer will be able to advise on the best heat pump for your property, but factors influencing the size of your heat pump may include:

For accurate heat pump sizing, get in touch with one of our Vaillant installers. They can perform a detailed heat loss calculation and recommend the best heat pump size for your home. They can also help with selecting the correct Vaillant heat pump, control and cylinder to help meet your heating and hot water requirements.

Find out more about how to buy a Vaillant heat pump.

Internal space needed for an air source heat pump

You will need interior space for:

• A hot water cylinder, like uniSTOR, which is compatible with Vaillant heat pumps (126.5cm H x 59.5cm W). If you are upgrading to a heat pump from a system or regular boiler, you will already have space for a cylinder.
• A heat exchanger unit which is roughly the size of a regular gas boiler (e.g. aroTHERM heat exchanger 50cm H x 36cm W)
• A heating control like the sensoCOMFORT (10.9 cm H x 17.5cm W)
• The myVAILLANT connect internet gateway (9.6 cm H x 12.2cm W) to allow full system control via the myVAILLANT app.

If you are installing a heat pump and are based in the UK, be sure to find out if you are eligible for a UK heat pump grant.

As of 2024, there are a range of grants available, including:

• Boiler Upgrade Scheme
• Energy Company Obligation Scheme
• Warmer Homes Scotland
• Home Energy Scotland Scheme

Properly sizing your heat pump is key for comfort, energy efficiency, and system longevity.

Consider factors like property size, climate, insulation, and usage to determine the right size for your needs. Consulting a professional ensures you get the best advice and most suitable heat pump. Whether installing a new heat pump or replacing an old one, taking these steps will help you achieve the best results.