New UK Government grant to install heat pumps

The UK government recently announced its latest grant scheme, called the Boiler Upgrade Scheme, that will help select applicants to replace fossil fuel-driven heating systems with heat pumps. What will the scheme provide, what are heat pumps, and are they a better alternative to heating than traditional gas boilers?

UK Government announces new Boiler Upgrade Scheme

On the 18th of March 2022, the UK government announced a new scheme that aims to replace fossil fuel heating systems with environmentally friendly solutions in domestic properties. The three main heating systems that are being offered via the new scheme are heat pumps, biomass boilers, and ground source heat pumps. Eligible criteria for the new scheme are that applicants own their property, and the grant offers £5000 for heat pumps and biomass boilers and £6000 for ground source heat pumps. Additionally, properties that apply for the grant must not have an installation capacity over 45kWth and require an EPC certificate that does not recommend additional insulation (loft or cavity).

The new grant is expected to help homeowners switch from gas boilers to environmentally friendly options to reduce carbon emissions. Furthermore, the UK government aims to ban gas boiler installations after 2025, which will help make the UK a net-zero carbon country by 2050. This move also coincides with the plan to ban the sale of new diesel and petrol vehicles by 2030, but whether this will be possible is still unknown (electric vehicles are still extraordinarily expensive and take a long time to charge). In total, the scheme has secured £450m in funding, which will provide up to 90,000 new boiler systems.

What are heat pumps?

Before exploring the efficiencies of heat pumps and whether they are an ideal solution for carbon reduction, we first need to understand what heat pumps are and how they work.

In essence, a heat pump is a device that can move thermal energy between two places. A classic example of a heat pump is an air conditioner that absorbs thermal energy from a room and then dumps that energy into the outside air. Another example of a heat pump is a fridge that extracts thermal energy from food and then expels that heat energy outside of the refrigerator.

Most heat pumps utilise a substance that can easily be compressed into a liquid and vapourised into a gas to transfer heat. The compression of a gas into a liquid increases the temperature of the liquid, while the vaporisation of a liquid into a gas causes the gas to decrease in temperature. As such, a fridge vaporises a liquid into a gas, uses the gas to cool down the inside of the refrigerator, and then compresses the gas back into a liquid which is then cooled down externally.

However, instead of thinking of a fridge as cooling down food, think of it as the food heating up the gas (the cooled gas is generally in the -40˚C temperature range). When the gas is recompressed, it becomes incredibly hot (far more than the surrounding ambient air), allowing the outside air to remove the extracted heat.

A heat pump designed to warm a house is very similar, but instead of removing heat from the house, it extracts heat from outside and brings it into the home. While it may seem counterintuitive, heat pumps can effectively heat up homes even during the middle of winter when the ambient temperature is below freezing. This is because the temperature of vapourised refrigerants is generally lower than -40˚C, which means that it can still be heated up by the relatively warm -5˚C air outside. So long as there is a sufficient temperature gradient between the vapourised refrigerant and the outside air, heat can be extracted.

Are heat pumps a better alternative to fossil fuel boilers?

While heat pumps sound good in principle, their use as a house boiler is highly dependent on the temperature outside, the technology used, and the cost of energy. Heat pumps used for homes generally have a COP between 3 to 4, meaning that for every one unit of energy consumed by the heat pump, it will be able to extract 3 to 4 times as much thermal energy from the outside.

But heat pumps require electricity to drive a compressor that is used to drive the refrigerants around the system, and it is here that things become grey. There is no doubt that heat pumps provide better carbon options as a typical gas boiler produces 215g of CO2 per kWht while heat pumps generate 11g of CO2 per kWht, but the reliance on electricity can make them costly to operate.

Gas has always been significantly cheaper than electricity per kilowatt-hour which is why it is favoured as a heating solution, and the price difference is generally around 2 to 3 times (12p for electricity and 3p to 5p for gas). As such, heat pumps will either be on par or more expensive than gas heating, but never less.

Of course, that may no longer be the case as utility prices continue to surge in light of the COVID pandemic, poor government planning, and the Russo-Ukraine war. While both electricity and gas have shot up, it may be that electricity prices will fall faster than gas as new energy sources are explored.