All-electric homes
It’s not a new idea, but perhaps it’s an idea thats time has come. Tim Pullen asks whether electricity could be the one-energy solution to our future needs
Ever since we realised that nuclear energy was not going to provide free energy for all, the all-electric house has been considered a daft idea. The shockingly low efficiency of fossil fuel power stations (less than 30%) leads to a high unit cost of electricity and, more latterly, a growing awareness of the impact of power stations on the environment. Rather than putting oil and gas into a power station, it made far more sense to burn those fuels in our own boilers and get over 90% efficiency. But, as always, things are changing. Prices have continued to rise, but the increase in nuclear power, wind and solar farms has driven the CO2 burden of grid electricity down to a point where it is now one of the lowest emitters. This means that the all-electric house – effectively one removed from mains gas, or an off-mains alternatives such as oil or LPG – no longer seems quite so beyond the realms of possibility. And the lower energy demands of thermally efficient homes makes an increasingly strong argument in favour of the all-electric house. The issue of running costs remains, but there are a number of ways of addressing it.
Power
Beginning in the 1930s, the amount of electricity consumed in the average house increased at a fairly steady rate. Then, in 2004, it started to fall, a trend that still continues despite the proliferation of electrical goods. The savings are almost entirely due to manufacturers making their goods more efficient rather than homeowners’ activities. Obviously using
energy-efficient appliances is a good start, but there are other things we can do to minimise electricity consumption: installing LED lamps, using power-down or smart sockets to switch off appliances that are not being used (these cost around £5 to £25), and installing a solar PV (photovoltaic) array to generate electricity on site, with a battery for storing it. Smart meters are also said to help, perhaps simply by focusing our attention on how much electricity we use.
Heat and hot water
The big issue for the all-electric house is heat. Let’s think about a 250m2 floor area house built to the 2000 Building Regs standard. It will need around 18,000kwh of space heating energy per year. That same house built to current standards would need little more than half of that. At Passivhaus standard the figure drops below 4,000kwh/year. Clearly, for the all-electric self-builder, the key to affordable running costs is to lower space heating demand of their new homes — namely by investing in insulation and airtightness.
The unit cost of electricity (the price per kwh) is undeniably higher than that of other fuels, but that does not necessarily translate into higher running costs for exclusively electric houses. Providing space heating and hot water to our 2000 Building Regs house via a gas boiler is likely to cost around £720 per year, assuming a 90% efficient boiler and a unit cost of 5.4p/kwh for gas*. An air source heat pump will do the same job for £548, assuming 350% efficiency and a unit cost of 16p/kwh for electricity*.
A heating distribution system and hot water cylinder will cost broadly the same whether you opt for a heat pump or a boiler, but an air source heat pump will cost in excess of £7,000 for our example
Clearly, for the all-electric house builder the key to affordable running costs is insulation and airtightness
Taken together these factors make a compelling economic case for going all-electric
house, while a gas boiler would only be around £2,000 to £3,000. However, the heat pump is likely to last twice as long as the boiler, there will be no gas connection fee and no standing charges. Taken together these factors make a compelling economic case for going all-electric.
On-site generation
Obviously, for the all-electric homeowner, generating as much of your own energy as possible is a good idea, but it shouldn't be taken as an essential requirement. The reality of most domestic situations is that solar PV is the only viable option for onsite generation; that it will be limited to around 4kw capacity and a battery system will be needed to maximise its value. Capital cost of such a system is likely to be around £8,000 giving a unit cost of around 13p/kwh over 20 years. The average price grid electricity is 15p/kwh (including VAT and standing charges) demonstrates that generating your own electricity is a good idea, but not essential.
In conclusion…
The government’s drive to meet their decarbonisation goals, as put into action by the Future Homes Standard and the ban on fossil fuel heating in new homes from 2025, means that the all-electric home is now an inevitability. There is talk of decarbonising the gas grid by using hydrogen or biogas, but that is still some distance from being a reality, leaving no alternative at the present moment.
The question for anyone planning to selfbuild in 2021 or beyond is whether to install a boiler or perhaps accept the direction of travel and build an all-electric house.