Net zero: heating

The shift to low carbon heating is at a relatively early stage compared with sectors such as power and transport. However, the technology needed to warm our homes without producing carbon dioxide is already in existence, and falling in cost.

There is a growing consensus that the decarbonisation of heat is vital to reaching net zero, through deployment of low-carbon technologies such as electric heat pumps, district heating and low-carbon gases, in combination with reducing demand through improved energy efficiency.

Heating is responsible for around 40% of UK energy consumption and 20% of emissions. Policymakers have identified heat as a 'difficult' area to decarbonise, due to large energy requirements (at peak, demand can be multiple times that of the power sector) and the extent to which points of emissions (such as boilers in homes) are locally distributed.

Home Radiator
Heating homes is a major source of carbon emissions.

However, there is no reason why emissions from heating buildings cannot be almost completely eliminated.

British homes generate the majority (60%) of heat demand. Since 1990 emissions from homes have fallen by 17%, largely due to more efficient boilers and better insulation, meaning we need to use less energy to keep warm - ultimately leading to lower energy bills.

Currently, 80% of UK homes are heated with natural gas – a higher dependency than many other countries. This can be traced back to development of North Sea reserves. As these dwindle, the desire to become less reliant on imported fuels to keep warm is another reason to decarbonise the UK’s heat supply.

Options

Despite slow progress in developing low carbon heat policy, the technologies needed to decarbonise the sector exist today. There are a number of options available, with the main source of uncertainty the extent to which each will be used.

Options include:

  • electric heating (usually via heat pumps)
  • adapting the existing gas grid to run on low carbon gas(es)
  • increasing the number of district heating schemes attached to a low-carbon heat source.

A heat pump is rather like a refrigerator in reverse - drawing heat from the ground or outside air, even when it is cold, concentrating it, and transferring the heat into the building.

Hydrogen could be a future substitute for natural gas in the gas grid and district heating schemes are commonplace in countries across Europe. District heating schemes are also known as heat networks – a central heat source that supplies multiple buildings via a series of underground hot water pipes.

The eventual solution is likely to involve two or three of these options, with the government stating 'it is not certain which approaches or combination of them will work best at scale and offers the most cost-effective long-term answer'.

As well as changing to modern technology, increasing the efficiency of the UK’s housing stock also has a major role to play. The UK’s housing stock is one of the least efficient in Europe, losing three times more heat on average than Swedish homes due to poor insulation. Cutting the amount of heat that escapes through roofs, walls and windows is widely acknowledged to be the logical first step in cutting carbon from heat.

The government is  developing a heat and buildings strategy, expected in late 2020, to inform the roll out of decarbonised heating systems during the early 2020s. The strategy will ‘set out the immediate actions for reducing emissions from buildings… (including) the deployment of energy efficiency measures and low carbon heating technologies’.

Forecasts

A 2018 review of the current evidence into the future of heat in the UK found three common messages:

  • demand reduction through improved efficiency is essential
  • there is likely to be a major role for electrified heat and hydrogen
  • district heating schemes attached to low-carbon heat sources will be in use.

The National Infrastructure Commission recently advised that low-carbon gas (principally hydrogen) and heat pumps need to be trialled as they are likely to play an important role, and all technologies will play some part.

Progress on cutting emissions from buildings chart
Progress on cutting emissions from buildings has been slow. Image: CCC

Modelling by the Committee on Climate Change (CCC) shows that all practicable lofts and cavity walls should be insulated by 2032, and that emissions from buildings will fall by a further 16% to 2030. It also says that 20% of the UK’s heat could be provided by heat networks by 2050, with the remaining 80% generated in the building where it is used by systems such as heat pumps. The CCC indicate that 1.1 million heat pumps will be needed by 2030 and 19 million by 2050 to reach our climate change goals.

A major factor in determining the best source of low-carbon heat is the number of other homes nearby, with those in more rural settings suited to heat pumps and those in towns and cities connected to heat networks. The population density at which it makes sense to switch between these technologies is one of the major decisions facing politicians and policy makers.

An advantage of low-carbon gas (biogas or hydrogen) is that it would reduce (although not eliminate) disruption to homes and businesses by making use of existing gas networks. Concerns over supply of both hydrogen and biogas may limit their use, however.

Decision time

Current action to decarbonise heating in the UK occurs via the Renewable Heat Incentive (RHI), which provides payments to homes and businesses to shift to non-fossil fuel heat sources. Currently, this is almost entirely met by demand from biomass (wood) and waste. The RHI will close in 2021, to be replaced by a Clean Heat Grant that offers upfront payments to offset the cost of technologies such as heat pumps.

The government released an 'overview of evidence' for heat decarbonisation in December 2018, in which it stated that clarity on the future of heat in the UK is expected in the 2019 Spending Review. This decision has now been pushed back, and is set to be part of the Heat and Buildings Strategy due in late 2020.

However, the government acknowledges that decisions need to be made in the next few years. With the solution expected to be a combination of reducing demand as well as decarbonising supply, the path to a zero carbon heating system will become increasingly clear.

Action on boosting building efficiency seems imminent, with political support from all major parties. In the 2020 Summer Economic Update, Chancellor Rishi Sunak pledged £3bn for improving the efficiency of homes and public buildings. The Government is also mulling tighter standards for new builds, although those proposed to date have been criticised for lacking ambition.

Measures to make buildings 'energy positive' - so that they generate more energy than they consume, as is happening in other countries - could also be replicated in the UK.

A national net zero emissions target would give UK industry a head start on a nascent global business, providing considerable export opportunities as other countries decarbonise their heating supplies.