How do solar panels work?

Step 1: light becomes DC electricity

A solar panel is a sandwich of silicon cells. When daylight — not just direct sunshine — strikes the silicon, it knocks electrons loose and creates a direct current (DC). This is the photovoltaic effect, and it works on a bright overcast day in Leeds as well as a clear one in Cornwall, just at lower output. Each modern residential panel produces around 430 watts at peak, and a string of them wired together forms your array, measured in kWp (kilowatt-peak: output under standard laboratory sun).

Step 2: the inverter makes it usable

Your home runs on alternating current (AC), so the DC from the roof passes through an inverter — a box in the loft, garage or on a wall — that converts it. This is also where most system intelligence lives: the inverter tracks the panels’ sweet spot as light changes, reports generation to an app, and shuts everything down safely if the grid fails (which is why standard systems go dark in a power cut — they must not energise lines engineers are repairing). Hybrid inverters also manage a battery, deciding whether surplus power charges the battery, heats water, or exports.

Step 3: your home uses it first

Electricity takes the shortest path. Solar power flows into your consumer unit and is consumed by whatever is running — fridge, router, washing machine — before anything is imported from or exported to the grid. Only the surplus leaves, through your smart meter, which records it for Smart Export Guarantee payments. That ordering is why self-consumption is worth 26.32p/kWh at the October 2026 price cap while exports earn 3–6p: the same unit, five times the value, decided by whether your dishwasher was running.

What about winter, night and clouds?

UK solar is strongly seasonal: a typical system makes roughly three-quarters of its annual energy between April and September. December might yield a tenth of June. At night, obviously, you import — which is the gap a battery fills, storing the midday surplus for the evening peak. None of this breaks the economics, because the annual total — an estimated 850kWh per kWp across the year — is what the payback maths runs on. Think of panels as a strong summer employee who does light duties in winter, not a boiler replacement.

The parts list, briefly

Panels (25-year performance warranties), mounting rails fixed to the rafters, the inverter (expect one replacement in the system’s life), cabling, and certification: an MCS-certified install gets you the certificate you need for SEG payments and any future buyer’s solicitor. That, plus scaffolding, is what the £1,565–£1,686 per kW installed price buys.