How do solar panels work? The full explanation, from photon to plug socket

The short answer

Solar panels work by using sunlight to knock electrons loose inside a layer of semiconducting material, almost always silicon, and the loose electrons flow in one direction as a direct current. That is the photovoltaic effect, and it is the only part of the process that involves any physics you have not met before.

Everything from that point on is ordinary electrical engineering. An inverter converts the direct current into alternating current at the voltage and frequency your house and the grid both run on. Then your consumer unit sends it wherever there is demand.

What is actually inside the panel

A panel is a grid of cells wired together behind glass. Each cell produces a small voltage, and wiring them in series adds those voltages up into something useful. The cell technology matters more than most sales conversations admit, and we cover the differences in panel types explained.

One number you will see on every quote is kWp, or kilowatt peak. It is the panel's rated output under standard test conditions, which include a cell temperature of 25C. British roofs rarely sit at exactly those conditions, so kWp is a comparison yardstick between panels rather than a promise of what you will see on a Tuesday in February.

From DC to something your kettle can use

The inverter is the component that converts direct current from the panels into alternating current compatible with household circuits and the grid. It is also the component that decides how much power your system can actually deliver at once, which is not the same as how many panels you have. That distinction trips up nearly everyone, and we unpack it in inverter sizing explained.

Once the electricity is AC, your home simply uses it first. Anything you are not using at that moment goes to a battery if you have one, and anything left after that flows out to the grid through your meter. Our battery storage guide covers what changes when you add storage to the picture.

Where each kilowatt hour ends up, and what it is worth

This is the part that decides whether solar is a good investment for you, and it has nothing to do with the panels. A unit you use yourself replaces a unit you would have bought. Under the Ofgem price cap for 1 July to 30 September 2026, the average capped electricity rate is 26.11p per kWh on direct debit. A unit you export earns whatever your export tariff pays, and on 3 August 2026 the widely available flat export rates sat between 3p for open-to-anyone tariffs and 15p for the best rates that only require you to take your electricity from the same supplier.

That gap is why battery storage, EV charging schedules and export tariff choice all belong in the same conversation as the panels. Our tariffs guide carries the rates with the date each one was checked.

Why the output moves around all day

Panels generate in proportion to light intensity, so they still generate on cloudy days and through winter, just less. Cloud cover does not switch them off, it turns them down. Our guide to cloudy days and awkward roofs goes through this in detail.

Temperature works the other way to what most people assume. Every panel datasheet publishes a temperature coefficient, and it is negative: the REC Alpha Pure-RX is quoted at -0.24% per degree, the Longi Hi-MO X10 at -0.26% per degree and the Jinko Tiger Neo platform at -0.29% per degree. Higher cell temperature means slightly lower output, so a bright cool day outperforms a bright hot one on the same roof.

Temperature coefficients from manufacturer datasheets for REC Alpha Pure-RX, Longi Hi-MO X10 and Jinko Tiger Neo, accessed August 2026.

Because output tracks the roof rather than the brochure, the only honest way to answer what your roof will produce is to model your roof. Every county page on this site carries a calculator built for that area, so start at your county page and put your own numbers in.

The part of the process you never see

Connecting a generator to the public network is regulated. The company that owns the cables in your street, your Distribution Network Operator, sets what you can connect and under which process. A modest single phase system is fitted first and notified afterwards, and larger ones need permission before any work happens. If none of that means anything yet, start with what a DNO is and then G98 versus G99.

In a standard installation carried out by an MCS-certified installation team for your area, the homeowner never files any of that paperwork. It is the installation team's job from application to commissioning certificate.

What to do with all this

1. Find your annual kWh from a bill. Everything else is sized against that number.
2. Work out how much of your usage lands in daylight, because that is the electricity worth the most.
3. Look at the roof second, not first. Orientation, pitch and shade set the ceiling.
4. Decide on storage before you finalise panel count, since it changes how much of your generation you keep.
5. Check the export tariff you would qualify for, because a 3p rate and a 15p rate are the same electricity.

Rates and specifications in this guide carry the date they were checked. Export tariffs can change with 30 days notice, and the Ofgem cap is reset quarterly.