Low Carbon Home Heating

Heating in buildings is the second largest sector for carbon emissions in the UK after transport and we need to reduce these urgently. What are the low carbon heating options for your home? For most of us there are two main pathways: electricity or low carbon gas. Electricity is already nearly as good as gas in carbon emissions and by 2050 it will be effectively zero carbon. Heat pumps are the most efficient form of electric heating, for most homes.There are also ways to make zero carbon gas, though this is not scalable to replace all our heating needs.

Electric heating options

Electricity on a standard tariff is much more expensive than gas. However, with a heat pump you should get three times as much heat as the electricity you put in, so this narrows the gap very considerably, while the storage options can be charged up on cheap off-peak power. Also, if you get off gas completely you don't have to pay the gas fixed charge which can save you £70-£100/year.

Electric radiators

  • Cost to buy: low
  • Cost to run: high
  • Good for: extra heat in small areas.

There are lots of kinds of electric radiators including infra-red panels and oil filled radiators. Make sure they have some kind of thermostat.

Storage heaters

  • Cost to buy: medium
  • Cost to run: medium
  • Good for: small houses and flats with little space.

Storage radiators charge up cheaply overnight and release heat when required during the day. Modern heaters such as Quantum from Dimplex are thermostatically controlled and adapt the overnight charge according to need.

Storage heaters only supply space heating so you will need something for hot water too. This could be an instant electric water heater or a conventional cylinder with an immersion heater. The cylinder takes up space but you can heat it overnight, like the radiators, so it is potentially cheaper to run.

Heat batteries

  • Cost to buy: medium
  • Cost to run: medium
  • Good for: small houses and flats which have wet radiators now (easier retrofit).

Heat batteries are a new kind of heating. They also store heat rather than electricity and you can charge them cheaply overnight like a storage radiator. However, rather than having one in each room you have just one to replace your boiler, supplying both your hot water and your wet radiator system. For example Tepeo make smallish heat batteries for a small houses or flats, while Caldera make large ones for large houses. These batteries are large. The Caldera one weighs 1.5 tonnes!

Heat batteries can also be used for hot water only alongside a heat pump or storage heaters providing space heating. Some heat batteries, such as Sunamp, can be charged from different sources of energy such as solar panels or a heat pump as well as electricity. Sunamp heat batteries are more compact (about 30% of the size of an equivalent hot water cylinder).

Heat pumps

  • Cost to buy: high
  • Cost to run: low
  • Good for: most reasonably energy efficient homes with existing wet radiator systems

A heat pump replaces your boiler. Their advantage is they are much more efficient; you should get about three units of heat from each unit of electricity from an air source heat pump. The extra energy comes from the air and is renewed by the sun.

There are other kinds of heat pump, some even more efficient, but not suited to all situations. With a heat pump you will need a hot water cylinder and to get good efficiency you will probably need to either upgrade some of your radiators or improve your home insulation and air tightness. You also need somewhere to put the outside unit. This is a permitted development if it is out of site and not too close to your neighbour.

Although heat pumps are expensive to buy there are subsidies available. Up to April 2022 there is the renewable heat incentive (RHI), which will give you an income over 7 years. After that there will be a voucher scheme called the Clean Heat Grant. It will give you £4000 towards installing the heat pump.

There is lots more about heat pumps on our heat pumps page

Gas heating options

Most of us currently use a gas boiler now, and it is possible to buy renewable gas - this is called bio-methane or just bio-gas. The hydrogen option is not available yet and will not be for at least 15-20 years, if at all.

Biomethane

  • Cost to buy: zero – use existing gas boiler
  • Cost to run: medium
  • Good for homes that are hard to convert to heat pumps.

The gas we use now in our boilers is methane gas. This can be made renewably from food and farm waste – called bio-methane. However supplies are limited, because we need land for food and other things. This means we will not be able to replace more than about 10% of the gas now used for heating with bio-methane. You can buy bio-methane now, from Green Energy UK. The current price is rather more than standard gas: about 4.5p/unit. There may be other suppliers too, but some of them are not truly green gas, they simply offset the emissions.

Hydrogen

  • Cost to buy: Too soon to tell
  • Cost to run: Too soon to tell
  • Good for: not available for at least 15-20 years – may never happen or only in a few areas.

Hydrogen is another option which is often discussed in the news. However, this possibility is not available now and will not be for decades, except in small quantities blended with methane in the existing grid. Hydrogen burns differently from methane and appliances would have to be adapted. It is possible to mix in up to 20% by volume of hydrogen with methane without changing appliances but since hydrogen has very low density, this provides only 7% of the energy value.

In the longer term, it might be possible to make hydrogen in large quantities and supply it through the existing gas grid (with some upgrades). However, since this would mean adapting all our appliances so they were ‘hydrogen ready’ first, this will take at least 15 -20 years. In any case, for a variety of reasons this is not truly sustainable in the long term at the scale needed to replace all our heating. See also Heat pumps or hydrogen

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