Glossary
Self-consumption
The share of your solar output that you use in your home as it's generated, rather than sending it to the grid.
Self-consumption is the part of your solar generation that your home uses at the moment it’s produced: the fridge, router and anything else running while the sun is out. Whatever isn’t used flows out to the grid.
For plug-in solar, self-consumption is where almost all the savings come from. Plug-in kits don’t normally qualify for the Smart Export Guarantee, because it needs an MCS-certified (or equivalent) installation and a half-hourly export meter (gov.uk). Exported power usually earns nothing. Kits with batteries are outside the GB rules (SI 2026/848), so you can’t store the surplus for later.
The share you use depends on how much electricity your home draws during daylight. DESNZ’s impact assessment estimated a higher share for a household that is home all day, and a higher share for a vertical east/west kit than a south-facing one, because its output is spread more evenly through the day (impact assessment, Table 7).
In practice, if you have a smart meter, your overnight “always-on” usage is a good guide to how much of a small kit’s output you’ll use.