The UK government has recently announced new grants to encourage the public to move from gas boilers to heat pumps, a greener energy alternative. But little has been said about electric boilers as another low-carbon option, writes , senior lecturer, School of Engineering, University of Portsmouth.

Low-carbon heating systems

The UK is aiming to phase out gas boilers and replace them with low-carbon technologies, such as heat pumps and electric boilers, in order to reach net-zero levels of CO₂ by 2050. Households are being offered grants of up to £5,000 for low-carbon heating systems with the ambitious target of 5.5 million heat pumps installed across Britain by 2030. There are currently no grants for electric boilers, but these could also help with the transition to low-carbon solutions for those in smaller homes.

In 2019, 1.7 million gas boilers were installed in the UK, nearly 2% more than in 2018. Gas boilers have long been consumers’ preferred option due to lower upfront and running costs, with 80% of UK homes currently relying on gas heating.

But electric boilers are extremely effective, all of the electrical energy they consume is converted into heat, unlike gas boilers, which are only about 95% heat efficient. They are also smaller than gas boilers and can be installed anywhere inside a home without a need for a flue pipe. While electric boilers are not designed to meet heating demand in larger homes, they are an ideal solution for flats and small houses.

While many people are put off by heat pumps because of all the changes needed, they might consider an electric boiler. An air-sourced heat pump requires space to install an outdoor unit, in addition to an indoor unit and a hot water tank (sometimes two).

Ground-source heat pumps require even more outdoor space and they are generally more expensive. This will pose a challenge in many older and smaller homes across the UK. There are also concerns about heat pumps causing extra noise.

Comparing heat pumps and boilers

Heat pumps are not a new technology, with various models and sizes available on the market and they are more efficient than gas boilers. They are designed to provide steady temperatures throughout the day, rather than 'when needed' use of conventional gas and electric boilers.

Heat pumps use electricity in a more efficient way. However, electric boilers have considerably lower investment costs because they are cheaper and simpler to install. Electric boilers rarely require any major construction work, such as installing new radiators and water storage cylinders.

With greater choice of gas boilers on the market at lower prices, electric boilers are rarely considered and some consumers are not even aware they are an option. Denmark is one country that has recognised electric boilers can be part of the green solution.

In Denmark, heat pumps and electric boilers have been part of the approach to decarbonising the heating network, with electricity mainly coming from wind power. Currently about 40% of Danish energy relies on fossil fuels, and the goverment’s intention is to become completely fossil fuel free by 2050.

Historically the cost of electricity has put UK householders off opting for either of these options, even though studies show that the cost of electricity from renewable energy technologies, mainly wind and solar, is going down.

Producing electricity from renewables used to be more expensive than burning gas. With improvements in efficiency and technology, the cost of renewables has significantly decreased in the past decade. And with growing demand, the prices will continue to fall.

Both heat pumps and electric boilers rely on electricity to operate. In addition to being generally more expensive than gas, some electricity still comes from carbon-intensive sources, making it less environmentally friendly.

In the second quarter of 2021, only 37.3% of generated electricity came from renewables due to unfavourable weather conditions, less sun and less wind than expected. Approximately the same amount of electricity was produced from fossil fuels, and the rest from nuclear energy sources.

To achieve the UK’s net-zero electricity target by 2035, significant renewable energy capacity additions are needed at the same time as closing coal-powered stations.

Effective solutions

With electricity provided from renewable and low-carbon sources, a combination of heat pumps and electric boilers for domestic heating and hot water production will cover our energy needs in a sustainable and climate-friendly manner.

While heat pumps and electric boilers are effective solutions in combating the carbon emissions, they are not the only electricity-hungry technologies increasing in use.

With multiple technologies relying on electricity, and with more electric cars on the roads, it is also essential that electricity production capacity is expanded via renewable and sustainable sources.

Electricity prices have been volatile recently and a rise in energy prices is one of the main concerns for UK consumers, particularly those thinking about moving to electricity-based heating. While prices spikes are likely in the immediate future, the market should stabilise in the long term.

Alerting people to a green alternative to heat pumps for heating their homes that doesn’t involve massive disruption and cost could well play a part in meeting our environmental targets ahead. 

This article first appeared in The Conversation, and was written by , senior lecturer, School of Engineering, University of Portsmouth.