How it works
How plug-in solar actually works in a UK home
No scaffolding, no roof penetrations, no export tariff. A plug-in system is a small, self-consumption-only generator — and understanding that shapes every other decision.
- 1
Sunlight hits the panel
One to four rigid or flexible photovoltaic panels convert daylight into direct current. Output is highest with unshaded, south-facing panels tilted towards the sun, and falls sharply in shade.
- 2
A microinverter converts it
A small grid-tied microinverter turns the direct current into 230V alternating current, synchronised with the mains. Its rated output is what determines whether a system counts as within the UK limit.
- 3
It plugs into a socket
The inverter connects to a standard socket circuit with a supplied lead. The electricity flows to whatever is drawing power in your home at that moment — fridge, router, standby loads, kettle.
- 4
Your meter sees less demand
You are not selling anything. You are buying less. Every kilowatt-hour generated and consumed on the spot is a kilowatt-hour you do not import at your tariff rate.
- 5
Surplus goes to waste (usually)
If your home uses less than the panels are producing, the excess flows out to the grid unmetered and unpaid. That is why daytime occupancy matters more than panel size.
The 800W limit, in plain terms
The figure that governs plug-in solar in the UK is the inverter's rated alternating-current output, not the total wattage printed on the panels. A kit can carry 1,000W of panels behind an inverter limited to 800W and still sit inside the limit, because the inverter caps what reaches your circuits.
This matters when comparing products. A listing headlined “1,000W solar kit” may be describing panel capacity. Always check the inverter's rated output before assuming a product is compliant, and treat any inverter rated above 800W as outside the scope of a simple plug-in installation.
What to check before you buy
- The inverter's rated AC output, in writing, from the manufacturer — not the marketplace listing headline.
- Whether the product is sold for the UK market with UK-standard plugs, documentation and conformity marking.
- Whether your Distribution Network Operator requires notification, and whether the seller handles it.
- Written permission from your landlord, freeholder or managing agent if you do not own the outside space outright.
- Whether your home insurer needs to be told about a fixed external installation.
- How the panels will be mechanically fixed, and what happens to that fixing in a winter gale.
Where the savings actually come from
Savings are the product of three things: how much the panels generate, how much of that you consume at the moment it is generated, and what you pay per unit. Get any one of those wrong and the payback stretches out considerably.
A household with someone home during the day, a heat pump or a well-programmed dishwasher can push self-consumption high. A household that is empty from eight until six will export most of a sunny afternoon's output for nothing.
What plug-in solar is not
It is not a substitute for a rooftop array. An 800W system in the UK generates roughly the annual electricity of a large fridge-freezer plus standby loads — useful, but a fraction of a typical household's demand. It is not a backup power supply, and it does not earn export income.