The electrification of heat
Rapid progress in decarbonising the UK’s power grid means that electricity is an increasingly low carbon source of energy. Using this to power heat generators is an alternative to fossil fuelled heat, and is seen by many as a vital part of heat decarbonisation. There are, however, concerns over costs, of upgrades needed for electric heat sources to operate properly, and over behavioural changes that will likely be needed.
Why electrify heating?
The theory of electrified heating is simple – use cleaner, renewable electricity to heat UK homes. The electricity grid is decarbonising rapidly (Figure 1), therefore emissions associated with electric heating are falling and will continue to do so. However, some argue that because the costs of electricity are currently higher than for gas, choosing electrification for heating risks increasing household energy bills.
The Committee on Climate Change (CCC) has identified that household electricity bills are often higher than gas bills because there are additional taxes and levies placed on electricity compared with gas. This includes support for policies to support renewable energy and to cut energy waste, as well as carbon taxes which are absent from domestic gas. To this end, the CCC, Citizens Advice, Policy Connect and Onward all recommend that this be reviewed.
There are several technologies that can electrify heating, some more proven than others. The Electrification of Heat Demonstration Project is currently underway, aiming to assess barriers to uptake of certain electric heating technologies on a household level.
Outside the home, widespread electrification of heat will require a number of infrastructure upgrades. Reinforced power grids, more generating technology and digital infrastructure to make the system smarter and more efficient will all be needed. This is comparable to issues associated with the electrification of transport.
Electric heating technologies
Electric (resistance) heaters
Resistance heating works by converting an electric current into heat using an electrical resistor. Some new homes in the UK already use electric radiators, while many more use portable heaters to provide additional heat during particularly cold weather.
Resistance heaters are nearly 100% efficient and like a gas boiler, are turned on and off as desired. Whilst this familiarity can be a benefit for consumers, it can also cause spikes in demand. And at the current costs of electricity, this type of electric heating can be expensive.
Electric storage heaters
Storage heaters generate heat through resistance before storing it in ceramic blocks to be released when needed. About two-thirds of the current electric heating stock in the UK is storage heaters.
The ability to store heat means they can run when electricity is cheapest and cleanest – generally overnight – but still provide heat when needed. This storage ability can also be used to balance the electricity grid, a potential source of revenue, or cheaper bills.
Heat pumps extract ambient heat in either the air, ground or water and raise it to a much higher temperature using a compressor and a condenser.
This concentration of heat means that heat pumps are highly efficient, producing three units of heat for each unit of energy consumed. Heat pumps are much more cost effective, and less carbon intensive than resistance heaters. They do, however, work best in well-insulated homes and are usually designed to run at lower temperatures but all the time, providing a different user experience than gas boilers.
While they are popular in some countries – France and Sweden each have about one million installed – there are only about 160,000 heat pumps in the UK, with installations running at about 20,000 a year. For comparison, more than 1.5 million gas boilers are installed each year in British homes, second only to China.
Industry experts agree that heat pump use is very likely to rise, with some estimating that 1 million will be needed annually by the mid-2030s. The CCC back this, indicating that 4 million heat pump installations could be required by 2030.
There is a growing consensus that heat pumps will be a major source of clean heat in the UK. Heat pumps are available to buy now, resulting in immediate emissions reduction. Low carbon gases, on the other hand, are still being developed.
An electrified heat pathway has the potential to create large carbon emission savings with some estimating in the region of 5 - 15MtCO2e (at the moment, the residential sector is responsible for 69.1MtCO2e per year). Although, this does come at a significant cost (£190 - £270 billion) when taking into account the upgrading and reinforcing of electricity grid infrastructure, as well as the heating systems within homes themselves.
The vast majority of net zero future scenarios include the electrification of heating to some degree, ranging up to a fully electric heating infrastructure with heat pumps the popular choice for most homes. The new ‘Green Homes Grant’ will also support heat pump installations, with a voucher of up to £5,000 for most homeowners available. With the heat pump industry claiming they are ready to deliver, and the Clean Heat Grant and Future Homes Standard coming into force over the next couple of years, significant growth in electric heating in the UK is expected.