Customers may have their own rooftop or other domestic generation facilities available to them. However, while domestic installations are included in the overall totals for our main substation, the initial version of Carbon Tracer does not take special account of individual circumstances. There are data protection regulations covering our customers, so we are unable to make use of the specific details at a single customer installation. The app also requires details of both demand as well as generation for the current, historical and future views, so the overall picture is much more complicated than might first appear.
The data used by the app is in fact based on the electricity mix at the level of the Bulk Supply Substation (BSP) which supplies a given area. The app totals up the values for the generation installations connected to our network under each BSP, usually at the 11,000 and 33,000 Volt levels. This includes (where they exist) large solar and wind farms, waste incinerators, hydro and wave power installations and several other types. The resulting energy mix that we determine for any given time is applicable to all customers served by that BSP. Where domestic generation is available, this will usually be consumed before any electricity is taken from our network, so the electricity mix at such places will usually be better in terms of renewables. A customer could potentially use the details displayed by the app to work out their own overall mix, but this would require them to know their load and generation levels at any given time and then do some complex calculations.