In the winter, a heat pump provides heating by extracting heat from outside a building and moving it inside. In the summer, it can provide cooling by moving heat from indoors to the outside.
Find out about the different types of heat pumps, how they work and why they could help to tackle climate change.
A heat pump uses the same technology as an air conditioner, which cools your home using a refrigerant. The only major difference between an air-conditioner and a heat pump is that a heat pump has a reversing valve, which allows it to also heat your home.
In heating mode, a heat pump works like an air conditioner in reverse; instead of keeping your home cool, it uses the refrigerant to warm your home.
Here’s a step-by-step process of how heat pumps work:
Heat could be sourced from the air outside or warmth from the ground. This is blown or pumped over the heat exchange surface of the exterior part of the heat pump.
This heat is warm enough to cause the refrigerant liquid in the heat pump to evaporate and turn into a gas.
This gas is then moved through a compressor, which increases the pressure, causing its temperature to rise.
The gas (now heated) is passed over the internal heat exchange surface. This heat can then be either blown around the home's interior or transferred into a central heating or hot water system.
As the heat is transferred into the home, the gas falls in temperature, causing it to return to a liquid state.
The cycle of reverse refrigeration repeats until your home reaches the required temperature setting on your thermostat.
Even when it’s very cold outside, some heat energy still exists. Heat pumps are effective at taking this heat energy from the ground or air around a building and using it to provide heat for your home or business.
For heat pumps to work at their best, it’s also important that the building has good energy efficiency installed, such as effective insulation.
There are different types of heat pumps: air-source and ground-source.
Heat pumps can also be paired with fossil fuel gas furnaces; these systems are often referred to as hybrid heat pumps.
Air-to-water heat pumps take heat from the outside air and feed it into your wet central heating system (similar to existing gas central heating). As the heat produced is cooler than that from a conventional furnace or boiler, you may need to install larger radiators or underfloor heating in your home to make the most of it. Air-to-water heat pumps may be best suited to new-build properties or those that are energy efficient.
Air-to-air heat pumps take heat from the outside air and feed it into your home through fans. This type of system can be used for heating but can’t produce hot water.
Around 40% of global emissions come from buildings and most of these result from the ways we heat our homes and businesses.
To reach net zero carbon emissions and tackle climate change, we need to switch from heating that relies on high-carbon fuels to cleaner, low- or zero-carbon alternatives.
Heat pumps will help to achieve this for two main reasons:
Heat pump systems are designed to extract a greater amount of heat energy from the surrounding environment than the energy they consume to create heat. They can produce two to three times more heat output than they consume in electricity input.
As more and more electricity is generated from renewable energy sources like solar or wind power, the electricity used to power heat pumps is itself becoming cleaner.
Last updated: 13 Apr 2023
The information in this article is intended as a factual explainer and does not necessarily reflect National Grid's strategic direction or current business activities.
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