Heating our homes
Today, you are likely to run your home heating system with a gas boiler, but will that continue to be the case in the future? National Grid’s Gas Demand Manager Stephen Marland looks at some of the potential alternative technologies and assesses the implications for our homes and the energy sector.
Over the past four decades, the gas boiler has been in the ascendency for home heating, but it wasn’t always like that. In 1970, fewer than 40% of homes used gas.
That all changed when newly discovered UK natural gas provided a solution for clean air and affordable central heating. Today, around 83% of us (or 23 million properties) use gas.
The way we heat our homes is a big item on the political agenda as the UK aims to tackle climate change and find sustainable energy without breaking the economy. So, are we about to see another revolution in home heating?
Gas boiler is benchmark
Heat is by far the most variable of our energy demands. An average house requires 12 megawatts a year (MWh/a) of heat compared to 4MWh/a for power demand. Due to the seasonal nature of heat demand, the peak in a day can be higher than five times what the power grid delivers. There are significant variations between buildings too. A new-build apartment may need only 6MWh/a, while a pre-war detached house could consume 30MWh/a or more.
Although the gas boiler has set the benchmark for what customers expect, there is a problem: gas homes still account for 70% of carbon emissions from the housing stock. Even with better insulation and more efficient boilers, this is incompatible with long-term climate change targets. Simply, we will need to use far less gas in the future.
Is electricity the answer? Switching to more electricity makes little sense today. It would be bad for the environment (generation is highly carbon intensive), bad for consumers (resulting in higher utility bills) and bad for the network (which is not built to accommodate large-scale heating). But it’s worth looking at the near-term products that could potentially change things.
I’ve yet to see a low-carbon 2050 scenario in which the market share of electrical heating does not increase significantly. The theory goes something like this: insulate homes to an economic level, de-carbonise the generation sector with nuclear and renewables, expand the capacity and displace heating in buildings with district heat networks or electric heat pumps.
The power distribution grid, and of course the generation market, would need to be significantly larger than today. This would take time to construct and possibly require long-term regulatory and cross-party political agreement to make it a reality.
We see the role of gas becoming increasingly important in supporting low-carbon intermittent supply of renewable power.
– Stephen Marland, National Grid Gas Demand Manager
A heat pump is the generic term for a range of products, such as ground, air or water types fuelled by electricity or gas. The most common and favoured politically is an electrical air-sourced heat pump. This is a fantastic product that can deliver typical efficiencies of around 200-400%. However, they take up more space than a gas boiler and require an outdoor unit like an air conditioner. They’re likely to remain a niche product unless prices fall sharply and products become more appealing to customers.
District heating has many advocates. Communal or district heating – the supply of hot water or steam from a network – currently serves up to 200,000 UK homes. These are mainly in urban centres, with networks slowly growing in parts of London, Manchester and other cities.
In principle, heat networks are the closest to what customers say they want, providing the running costs can match gas. On the down side, the market share is less than 1% of UK homes, and putting in place the necessary infrastructure will take time and could be expensive.
Furthermore, there will be a real challenge in scaling up economically with a sustainable fuel supply, and how would we make the hot water or steam to start with?
Most studies to date predict heat networks will serve upwards of 10-15% of our demands in the future – they are perhaps part of the solution depending on where you live.
New kids on the block
The high efficiencies of heat pumps are a major advantage and can keep running costs comparable to a gas boiler. However, the upstream infrastructure, low-carbon generation and grid reinforcement, will push up costs, especially if they are designed for the peak seasonal demands.
A better economic solution makes use of a ‘hybrid’, a smaller scale electric heat pump (for baseload heat) combined with an existing gas boiler (providing top up heat on colder days) – a scaleable, residential smart grid set-up. With these products, generation capacity and costs are minimised. Such products ought to go on sale this year from a range of well-known manufacturers.
Other products to look out for are gas heat pumps, which are at the prototype stage in the residential market. The efficiencies are lower at 115-165%, but still a substantial improvement on boilers. They are likely to feature outdoor units like air-sourced heat pumps, but the internal units are expected to be similar to a boiler in size. Running costs are the key advantage of a gas heat pump and fit with the current infrastructure, so there will be no need for additional power stations or networks to be built to support the roll-out.
The right balance
Getting the balance right will be a challenge if we want to have secure, affordable and sustainable energy in our homes of the future. I suspect that, in 10 years, most of us will still be using a gas boiler for heating, but it will be interesting to see how technologies emerge and whether government, regulators and the market will pull together towards a common vision.
As our rapid conversion to gas since 1970 has shown, a revolution can happen and markets can change fast, but are we really seeing the same ‘perfect storm’ conditions on the horizon?