Gas boilers banned in 15 years, but what will replace them?
How will we heat our homes in the future?
A new Energy White Paper* published by the Government gives the 'mid-2030s' as the date for no longer fitting gas boilers in existing homes. (A White Paper is proposed legislation.) This is the clearest indication to date of when gas boilers will be banned. Similarly, the Committee for Climate Change assumes a phase out date of 2033 for gas boilers and 2028 for oil and coal-fired boilers**.
The Energy White Paper expects that by around 2035 all newly installed heating systems will to have be low-carbon, for example heat pumps, which effectively bans gas boilers, although it may leave the door open for hydrogen boilers. Just to be clear, that does not mean you will have to remove a working gas boiler in 2035, but you will not be able to replace it with another gas boiler.
However there is no clear or single strategy for replacing gas boilers in existing homes. The next ten years will see a huge, national programme of whole-house retro-fit, whereby homes will need to be highly insulated to reduce our heat requirement to a minimum. This alone will reduce our gas consumption and opens up more opportunities for low carbon technologies to heat our homes.
But there is no one perfect replacement for gas boilers and no simple way of weaning ourselves of this cheap, easy and compact heat source. In this blog I review the alternatives to gas boilers, their efficacy and their suitability. The future of heating for you will come down to what type of property you are living in, so I also give some example timelines for properties of different ages and types.
A note on efficiency
It does not matter how good the technology is on paper; if the installation is inadequate the heating system will not operate at peak efficiency and the potential economic and environmental benefits will never be fully realised. Many air source heat pump owners have suffered high fuel bills because the technology was unsuitable for their home and/or it was poorly specified.
As we move forward, we cannot rely on 'renewable' heat sources to do all the leg-work straight out of the box and repeat the mistakes of condensing gas boilers where we collectively waste enough energy to heat Wales annually. It will be better to fit 300,000 heat pumps correctly than fit 600,000 heat pumps poorly and waste energy through inefficiency. A major programme of up-skilling is needed now to meet the demand for correctly fitted renewable systems.
The current options:
A phased approach to removing gas boilers is vital if we are to successfully transition to zero carbon homes without making costly mistakes. It is absolutely a 'fabric-first' approach, i.e. insulate homes first to reduce our heat requirement, followed by replacement of our gas or oil boilers at a natural point to avoid scrappage.
I am 100% behind the drive to renewables, but I do not believe in removing functioning equipment. The environmental cost of manufacturing heat pumps, shipping them across the world, the current skills gap that will lead to inefficiencies and the current high cost of installation must determine the right time for replacement.
The efficiency of heat pumps is only going to improve over time and the cost reduce, therefore for many households it will be better to wait. New gas boilers that are setup to run efficiently and use hydrogen mixes are still a good short term step to decarbonising older homes whilst they are insulated.
Whilst we can speculate about that replacement technology might be, the reality is that the ‘silver bullet’ technology may not have been invented yet. The following technologies are possibilities based on what we know now:
Hydrogen boilers look and operate like our existing gas boilers so at the consumer end this would be the simplest to switch to.
Hydrogen gas is made by splitting water into hydrogen and oxygen. The most common process for creating hydrogen is to use fossil fuels or electricity to split the molecules, however this reduces its capacity to be fully renewable and as such it is considered to be low carbon rather than zero carbon.
In the short term tests have found that 20% hydrogen gases can be added to our existing gas supplies and work with our existing boilers. However, this does not mean our greenhouse gas emissions are reduced by 20%. As hydrogen currently uses electricity or gas in its creation, the net reduction is more like 6-10%.
Whilst hydrogen mixes can form part of the transition to decarbonising homes, alone it does not present a comprehensive solution for the long term and is likely to be a transition technology with a few exceptions. The Committee for Climate Change estimate that only 11% of households may use hydrogen boilers and only where they are located near to industrial clusters also using hydrogen.
The future could be creating 100% hydrogen gas using much lower carbon production processes such as solar light energy produced by solar panels or 100% renewable electricity, but this technology is in its infancy.
The danger of hydrogen however is that is masks the inefficiencies of existing gas boilers. Almost all gas boilers underperform 10-25% on their A-rated label efficiencies. This energy waste must be rectified for existing boilers and not allowed to carried over to hydrogen boilers.
Air source heat pumps
Air source heat pumps are air conditioning units in reverse, the same as fridges. They take latent heat from the air and compress it to raise its temperature. This heat is transferred to a chemical called a refrigerant which - via a heat exchanger - will heat your radiator/UFH water.
Heat pumps run on electricity, but if set up correctly can generate 3-4 units of ‘free’ energy for every one unit of electricity. As more of our electricity is generated by renewable processes, such as wind farms, so heat pumps offer the biggest leap to reducing greenhouses gases from our homes.
They are not without their drawbacks however. The external unit is large and we are likely to have to give up our airing cupboards again to a large hot water cylinder. As such they are not currently that suited to small homes, although the roof space is an option.
Without retrofitting large amounts of insulation, they currently best suit houses built after 2000. Heat pumps are at their most efficient when running at low temperatures, which are too low to heat older properties without replacing all the radiators as well.
As our properties are become better insulated, and if heat pumps can get a little less space hungry, so they might prove suitable for older homes too. The Committee for Climate Change state that 5.5 million heat pumps need to be fitted this decade, around 2.2 million will go into new build homes and 1 million into off-grid homes. For more on heat pumps see our ultimate guide to air source heat pumps.
Solar thermal panels (that heat hot water) are by far the most efficient energy source available. Via pipes in the panel, the sun heats water that is pumped through the pipes and directly transferred to heat water and/or radiators if set up to do so. However this is energy that cannot be stored, i.e. if you are at capacity for hot water then the panels will 'stagnate'. Solar panels work best when combined with other renewable sources.
Solar PV panels (stands for photo-voltaic) produce electricity. They are much less efficient, however households can harness electricity all year round for appliances that are always on (for example fridges) and with battery storage can store surplus electricity for when it is needed.
For smaller homes, once retrofitted, it may be possible to use a combination of solar thermal and PV panels, with back up immersion, to provide enough energy to heat our homes. For larger homes they can form part of a mix of renewable sources that offer different benefits at different times of the year.
Hybrid heat pumps
Hybrid heat pumps combine a fossil fuel boilers (oil or gas) with a low temperature air source heat pump. The gas or oil boiler is used to top up the low temperatures supplied by heat pumps to meet the heating demands of the home where a heat pump cannot do it alone.
Heat pumps work best in well insulated properties and with underfloor heating systems. For low temperature heat pumps to work in our older housing stock, the property either needs to be massively insulated or the radiators need to double or treble in size.
Hybrid systems, often retaining the existing gas boiler, mean that older houses can begin to decarbonise their homes before insulation measures are fitted and remove the gas boiler at the end of its life and after retro-fit insulation has taken place. The Committee for Climate Change view hybrid systems as a key method to decarbonising our homes over the next decade. For more see our Guide to hybrid heating.
Property scenarios and timelines
The following scenarios show an indicative timeline for converting our homes to zero carbon by 2050 according to age and type.
Smaller, older properties will struggle to find space for air source heat pumps and more specifically larger radiators. They will likely be the last to fully decarbonise as we wait for a fully hydrogen boiler or effective insulation measures that cut the heat requirement to run the existing radiators at lower temperatures.
For terraced houses a whole-terrace approach will likely be needed for external insulation which could reduce the heat requirement sufficiently that an array of solar panels with a back up electric immersion (powered by renewably generated electricity) would be enough.
Larger homes and newer homes could convert to heat pumps much sooner and transition via hybrid heat source, that combines an existing gas boiler using 20% hydrogen gas with an air source heat pump.
2-3 bed mid-terrace Victorian house or older
2020-2030: 300mm loft insulation, floor insulation, double or triple glazing and sealing doors/windows from drafts. Correctly set-up (hydrogen- ready) gas boiler with load or weather compensation controls to run at A-rated efficiencies.
2025-2035: External wall insulation for the whole terrace with mechanical heat recovery ventilation to prevent overheating. Solar PV panels with battery storage and/or solar thermal panels either of which can be used to heat the home.
2035-2040: Replacement of gas boiler at the end of its natural life with standalone air source heat pump (space permitting) or a fully hydrogen boiler should the technology prove viable.
3-4 bed 1930s-1950s semi
2020-2030: 300mm loft insulation, cavity wall insulation or external wall insulation with mechanical heat recovery ventilation, floor insulation (where the property has suspended timber floors), double or triple glazing and sealing doors/ windows from drafts. Correctly set-up (hydrogen ready) gas boiler with load or weather compensation controls to run at A-rated efficiencies
2025-2035: Replacement of gas boiler at the end of its natural life with air source heat pump, solar PV panels (to create electricity) and/or solar thermal panels (to generate hot water).
4-5 bed detached or semi 2000 onwards
2020-2030: retrofit as necessary (some homes not built to A-rated standards): 300mm loft insulation, cavity wall insulation or external insulation, mechanical heat recovery ventilation and double or triple glazed windows and doors.
2025-2035: Air source heat pump, solar PV and/or solar thermal panels
Blocks of flats
Flats will require a whole-block approach to insulation, with the costs most likely split between the freeholder and flat owner, and district heating. Combined heat and power units - that produce heating and electricity - are a transitioning set up that will be replaced with water and sewage-source heat pumps and waste heat from industrial sources.
Alternatively, electric boilers can be used in some circumstances. Whilst they are not classed as renewable, they do have the potential to run on 100% renewable electricity.