Plug-in solar

What is it?

A plug-in solar kit is one or more small solar panels wired to a "microinverter" that plugs directly into an ordinary wall socket using a standard UK plug - no rewiring, no consumer unit work, and (for a suitable existing installation) no electrician required. While the panels are generating, the power feeds straight into whichever appliances in your home are switched on at that moment - a kettle, a fridge, a TV - reducing how much you import from the grid. There's no export payment mechanism for these small unmetered systems: electricity you generate but don't use at that instant flows out onto the grid the same as any small grid-tied inverter's would, but there's no metering or tariff set up to pay you anything for it, so from your point of view it's simply wasted - which is why how much time you spend at home during daylight hours matters as much as panel size for how much you'll actually save.

This is a distinct, much smaller-scale product from a full rooftop solar PV installation (typically 3-5kW, professionally installed, MCS-certified, often paired with a battery and an export tariff). Plug-in kits are capped at a fraction of that size by design - see Certification for how the two schemes differ - and are aimed at renters, leaseholders and anyone who wants a small amount of self-generated power without a full installation.

Why the power gets used by your home, not the grid

Your appliances don't "choose" solar power over grid power - electrically, there's nothing for them to choose between. What actually happens is simpler: your plug-in kit's inverter and the incoming grid supply both feed the same shared ring circuit that your sockets are wired to, and your electricity meter only counts whatever actually crosses it on its way in from the grid. Whatever the inverter is generating at a given moment is drawn by whatever's switched on in your home before anything needs to cross the meter at all - so it's "used first" simply because it never had to travel that far.

Simplified illustration: both sources feed the same ring circuit, so demand is met from whichever supply is available at that instant. The meter sits on the grid side only - it has no way to "see" what your panel is supplying, only what still has to come from the grid to make up the difference.

A worked example: if your kettle and fridge are together drawing 900W and the panel is putting out 400W at that moment, your appliances still draw 900W in total, but only the remaining 500W is pulled from the grid and shows up on your meter as import - the other 400W simply didn't need to come from there. It works the same way in reverse: if your home is using less than the kit's output - say it's putting out its full 800W maximum but your home is only drawing 300W at that moment - the other 500W doesn't just disappear. Like any small grid-tied inverter, it flows out through your supply onto the wider grid. But it isn't banked or paid for: there's no metering or export tariff set up for a kit like this, so that exported 500W earns you nothing - it's neither used nor rewarded. That's a separate point from anti-islanding (see Safety), which only acts if the inverter loses its connection to the grid altogether - it isn't there to stop export during normal, connected operation. This is also why how much time you spend at home during daylight hours has such a big effect on your actual savings, independent of panel size or location.

How much sun does Great Britain actually get?

The single biggest factor in what a plug-in kit generates isn't the kit at all - it's where in the country you are and what month it is. "Peak sun hours" is the standard way solar output is measured: one peak sun hour equals 1 kWh of solar energy per square metre, roughly what you'd get from an hour of a clear midday sun. Averaged over a full year, Great Britain gets nowhere near the Sahara, but it's also not as bleak as reputation suggests - southern England receives roughly four times as much irradiance in June as it does in December, and the north-south spread across the country is about 28% at the winter low point.

Illustrative monthly solar irradiance for London (kWh/m²/day, 20-year satellite average). Full location-by-location data, for ~20 UK towns and cities, is built into the Energy calculator.

Source: sunhours.app: UK solar hours by region (20-year, Jan 2001-Dec 2020, satellite-derived irradiance climatology). Last checked: 20 September 2026.

Sources

• GOV.UK: Plug-in solar - regulatory amendment and interim product specification (DESNZ consultation, government response and Interim Product Specification v2.0, July 2026) - the primary source for the technical limits covered across this section.
• sunhours.app: UK solar hours by region - the irradiance climatology behind the chart above and the Energy calculator.
• Sunsave: How much electricity do solar panels produce? - UK regional solar yield cross-reference.

This page is informational, not financial or electrical-safety advice. Always check a specific kit against the live ENA register (see Certification), and get a qualified electrician's opinion if your consumer unit is old, your circuits are unidentified, or anything about your installation looks unusual, before fitting one yourself (see Considerations).