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How do heat pumps work?

Part 1 of a 5-part series

The UK government wants people to replace their old boilers with heat pumps. In a bid to incentivise people to make the switch, households will be offered £5,000 grants from next April. But what exactly are heat pumps and how do heat pumps work?

A heat pump follows the same principle as your refrigerator. Simply put, it takes air from its surroundings then heats it, before pumping it around your home.

The components of a heat pump

There are two main components in a heat pump. The outdoor unit contains a coil and a fan. The fan blows air over the coil, which evaporates the air. The second main component, the indoor unit, also contains a coil and a fan. Here, the coil condenses and warms the air and the fan moves it over the coil and around your home.

Heat pumps contain refrigerant, a substance that melts and cools in relationship to the air. The compressor works with the refrigerant, helping move air through the system. Heat pumps also contain a reversing valve which enables the pump to cool your home in summer. An expansion valve regulates the refrigerant as it flows through the system. But how do heat pumps work?

How a heat pump works

Heat will naturally flow into cooler areas with less pressure. A heat pump works by connecting heat with cooler, lower pressure climates.

  1. The heat pump extracts heat from the air, ground or water around your home.
  2. At this point, the air is still cool. But it’s warm enough to turn the refrigerant liquid inside the heat pump to gas.
  3. The gas moves through a compressor and warms up.
  4. The warmed gas can then either be blown around your home or utilised by your central heating or hot water system.
  5. This cycle continues until your home is sufficiently warm.

It sounds pretty simple. And a £5,000 grant is certainly appealing. But energy and sustainability experts say the government is not going far enough to help homeowners become energy efficient.

Next week we discuss the pros and cons of heat pumps and whether they are indeed good for the environment.