A recent report, “UK housing: Fit for the future?“, suggests that houses built after 2025 should not be connected to the gas grid. This would effectively ban householders in new homes from using gas boilers for space and water heating and using gas hobs for cooking. The report suggests that alternative technology, such as heat pumps powered by electricity, would be used for space and water heating with electric induction hobs used for cooking.
The report was produced by the Committee on Climate Change (the CCC), an independent, statutory body established under the Climate Change Act 2008. The CCC’s purpose is to advise the UK Government and Devolved Administrations on emissions targets and report to Parliament on progress made in reducing greenhouse gas emissions and preparing for climate change.
CCC report that “Energy use in homes accounts for about 14% of UK greenhouse gas emissions. These emissions need to fall by at least 24% by 2030 from 1990 levels, but are currently off track. In 2017, annual temperature-adjusted emissions from buildings rose by around 1% relative to the previous year.“
Is Banning Boilers And Using Heat Pumps the Right Approach?
Whilst it is certainly headline grabbing, the potential switch from gas to electric space heating (using heat pumps) is really only a small part of the carbon reduction story. It will make the heating industry sit up and take notice but likewise a degree of caution is required. There are other potential heating technologies that could deliver some or all of the desired outcomes. UK citizens and tax payers should rightly get nervous when their government backs a particular developing technology as the winning solution. Governments of all persuasions have a poor track record on picking the right technology; the development of supersonic planes, nuclear power stations and diesel cars spring instantly to mind.
Government does have a role as an enabler in encouraging innovation at a small scale, until a technology is suitable for commercial exploitation, when it can then fight it out with other forms of technology in the marketplace. The main job of government should be to set and enforce decent energy performance standards for the construction of new housing and oversee the upgrade of the existing housing stock of 29 million homes.
The key issue to address is that we need new and existing homes that are both better insulated for warmth in winter and better equipped to cope with rising summer temperatures. Homes should also be equipped with more efficient lighting and appliances. Well designed homes, such as those designed to meet the Passivhaus standard, do that today. Building to this standard could reduce domestic energy consumption by upwards of 70%, using technology we have already available to us.
Table 1 below illustrates the point, using three different building and appliance standards:
- Current level: the current typical UK house
- Improved Insulation: a home built to Passivhaus standards. (See article on Energy Efficient Homes for more details on Passivhaus)
- Banning Boilers: a home using the Passvivhaus standard but with a heat pump for space and water heating rather than a boiler.
TABLE 1 : Energy Use In Typical UK Home By Application (kWh)
|Energy Use||Current Level||Improved Insulation||Banning Boilers|
- Current level: The energy demand of the typical UK house is around 17,100 kWh per year.
- Space and water heating (mainly from a gas boiler) account for 80% of domestic energy usage.
- Improved Insulation Option: By building to a higher standard, annual energy demand for the typical home could be reduced by around 10,000 kWh (58%) to around 7,100 kWh. Gas use would reduce by 70% and electricity use would rise by 4%.
- Building new homes to Passivhaus standard would reduce space heating demand by 87%. To meet Passivhaus the maximum space heating demand is 15 kWh per m² per year.
- Better insulated hot water tanks reduce energy demand for water heating by 23%.
- Appliance energy demand rises slightly to power a Mechanical Ventilation and Heat Recovery (MVHR) system, needed with a Passivhaus design. The system provides fresh air to the whole house and removes damp stale air. (See MVHR explained for more details).
- Lighting energy demand is reduced by the use of natural light where possible and switching to LED lighting where required.
- Banning Boilers Option: By incorporating the benefits of improved insulation and also switching to a heat pump, domestic energy use could drop by a further 34% to around 4,700 kWh.
- For space heating, air source heat pumps can deliver a Coefficient of Performance (CoP) of around 3.5. This means the heat pump can deliver 3.5kWh of heat for every 1kWh of electricity used (getting more energy than you put in may sound too good to be true but the extra energy is actually extracted from the outside air)
- For water heating, heat pumps have a CoP of around 2.6 so the savings are slightly smaller than for space heating.
What Does The Energy Use Data Tell Us ?
Table 1 tells us that by far the biggest fall in domestic energy demand, a saving of nearly 10,000 kWh per house per year, is driven by building to a higher energy standard NOT by switching to heat pumps and banning boilers. Banning access to the gas grid saves around 2,450 kWh per year, which is significant but nowhere near the level of benefits delivered by the better build standard for houses. Building homes to keep occupants warm in winters and cool in summer should be the priority for government policy makers.
Alternatives to Banning Gas Boilers
A 70% drop in a home’s gas demand from a better build standard does mean that today’s boilers could end up being vastly over-specified and this has consequences for boiler manufacturers. Who needs a 20kW power output boiler when a home’s heat demand may be nearer 2-3kW. This does create an opportunity for products like heat pumps to take share from gas boilers. Provided electricity is no more than 3.5 times the price of gas (matching the Coefficient of Performance of a heat pump) and the installation costs are at least on a par with a gas heating system, then gas boilers should decline in popularity through simple economics – not a ban. Let the best technology win!
Of course using natural gas, even at reduced levels, still produces carbon dioxide emissions The CCC assume that the carbon intensity of electricity will drop below 100g of CO2 per kWh by around 2028 and be close to zero by 2050. How can a gas boiler compete with that in the long term?
Well there are potential solutions which could help without writing off the huge investment in the existing gas network. In the short term, there are investigations into allowing upto 20% hydrogen into the natural gas grid from the existing level of 0.1%. Burning more hydrogen and less carbon would automatically reduce the carbon intensity of gas (natural gas is about 220g per kWh) without modification of existing gas boilers. If the hydrogen is produced by the electrolysis of water (splitting it into hydrogen and oxygen) using excess renewable electricity then there are few carbon emissions.
In the longer term, consideration is being given to switching the natural gas grid over to 100% hydrogen. That would require a change to gas appliances but this has been done in the past, when the UK switched from syngas (a mix of hydrogen and carbon monoxide) to natural gas (mainly methane) in the 1960s and 1970s. It is debatable whether all the hydrogen could be made by renewable energy at affordable prices. However with the development of effective Carbon Capture and Storage systems it may be possible to produce this hydrogen from fossil fuel sources for a decade or two until volume renewable hydrogen is fully competitive. An additional benefit to the 100% hydrogen approach is that the gas grid could run a fuel cell for co-generation of both heat and electricity for the home.
Why Are We Not Building Houses With Better Energy Performance Today?
A very good question. If government want to ban something then building homes with poor energy performance would be a very good place to start. Most house builders could switch to producing highly energy efficient homes, if we got serious as a nation about it. They don’t bother as it is not easy to do short term and requires investing in building some new workforce skills; builders are happy with the position they are in today making good profits building to the minimum (building regulations) standard. They spend some of that profit lobbying government not to improve building standards, arguing that it would push up the cost of buying a new house. This is true to a point. The point being that the energy costs of running a new home with poor energy efficiency are much higher than they should be. Homes built to be more energy efficient can cost more, but should give an overall saving for the homeowner with much reduced energy costs year after year.
Are the CCC right to think of banning gas use in new homes?
Simply put, No! Whilst it could be considered a well meaning attempt to save the planet from climate change, it goes the wrong way about addressing the issue. Heat pumps could well be part of the answer but then again they may be the next government technology mistake. The CCC seem to assume that, by threatening to prevent connection to the gas grid, house builders will try to build homes with better energy performance. However, this naive approach risks lumbering homeowners with homes that have poor energy performance which may be partially compensated for by heat pump technology. Making the current generation of boilers obsolete by making sure they are no longer needed would be the better approach.