5. Home energy supply

This option is more difficult to specify due to the complexities of grid-supplied electricity and gas in the UK (and in most other nations). However, our suggested targets and actions are, we think, the best way for consumers to deal with the imperfections of the current situation.

The first step for this option is to sign-up for a 100% renewable electricity tariff with a grid supplier that uses stringent certification standards. Ethical Consumer (2021) has pointed out how many certification schemes fall short, and concludes that only a small number of companies reach these standards, including Good Energy and Ecotricity (both of which exclude generating electrical energy from biomass due to questions over its carbon neutrality). Uswitch runs a green accreditation scheme also with the aim of independently verifying energy company claims. Berners-Lee (2020: 51–52) discusses the complexity of this issue further.

For the second step, we give different options for those who are tenants and those who are homeowners.

Tenants generally have much more difficulty in upgrading their home than owners due to the need to convince a landlord to invest in key measures. So, to meet the home energy supply target as a tenant living in a home with a boiler fuelled by fossil gas (‘natural gas’), we suggest that you sign up for a ‘green gas’ tariff with your supplier. Such a tariff relies on the supply of an equivalent amount of biomethane to the grid. As with the green electricity tariff, only suppliers who meet stringent certification standards are acceptable in order to meet the target (Ethical Consumer, 2021). Please note, however, that the sustainable resource of 'green gas' is probably small and there are significant controversies surrounding a large expansion. 

Hence, for homeowners, we recommend different options for this second step. As mentioned in the extra information for target 4 (home energy use), the current leading option for very low carbon home heating is to switch to a heat pump which is then supplied by electricity bought using a 100% renewable energy tariff. However, given that there is still a major need to rapidly expand the renewable sources supplying UK homes via the electricity grid, to meet the target in this section, we also recommend the installation of solar photovoltaic (PV) panels on your roof where practicable.

A common size for household solar PV arrays is 4 kW. This would (in average UK conditions) supply about 4,200 kWh/y (Berners-Lee, 2020: 142–144) – half of the approximately 8,400 kWh/y that an average household would use under target 4 above (3,500 kWh/y per person multiplied by 2.4 people per household). With grid electricity – via a renewable energy tariff – making up the difference (and playing a balancing role, for example, when the sun is not shining), this effectively reduces the direct carbon emissions of the energy supplied under target 4 to zero.

However, there are also lifecycle carbon emissions to consider, for example, the manufacturing of the solar panels and their associated electrics. But it is questionable whether these emissions should be counted within your lifestyle carbon footprint, as they are effectively contributing to national infrastructure and, by installing them, you are helping the government and energy industry increase its generation capacity. Also, using the electricity generated by the solar panel in your house means lower electricity transmission losses in the grid. However, the situation is in practice more complicated than this.       

To account for the complexities of electricity generation, we include an estimate for the lifecycle emissions in proportion to the level of your home energy consumption. We assume that, averaged across all households, these are the same for both tenants and home-owners. In target 4 above, we included an estimate for lifecycle emissions of the grid of about 20% per kWh i.e. 42 gCO₂e/kWh which – for an annual consumption of 3,500 kWh – results in 0.15 tCO₂e per person for the year 2021, and declines thereafter. (If you do not sign up for target 4, then your emissions for target 5 would be this lifecycle emissions estimate of 42 gCO₂e/kWh multiplied by your higher level of electricity consumption.)

Other very low carbon options for home energy supply are available, including:

• Solar hot water panels;
• District heating network fuelled by local renewable energy sources;
• Electricity via a private wire supplied by local renewable energy sources.

We will consider those on a case-by-case basis – so please contact us with your suggestions.

A further option is the use of wood fuel for home heating. However, questions over the carbon neutrality of the fuel (e.g. Physics World, 2020) – as well as its other environmental impacts (e.g. Air Quality Expert Group, 2017) – mean that we cannot make a straightforward recommendation for this option’s inclusion within our targets. It could potentially be included as a bespoke option as long as there is sufficient consideration of carbon neutrality, biodiversity, and air quality issues, including: the source of the wood fuel (e.g. whether it is from local/ managed/ certified sustainable sources); the quality of the wood fuel (e.g. whether it is in the form of logs, chips or pellets, how it is stored, and its moisture content); the quality of the wood fuel appliance (e.g. whether it is Eco-design directive compliant); the location of your home (e.g. urban or rural); and the health conditions of the home occupants (e.g. are any members of a vulnerable group such as people with asthma). A further issue is how to measure energy consumption (e.g. fuel weight per year or some sort of heat metering).

Again, please contact us with your suggestions.