How do solar panels work?
Solar panels do something that sounds like magic and is actually simple physics: they turn daylight directly into electricity, with no moving parts and no fuel. Understanding the basic chain, from sunlight hitting the roof to power flowing into your kettle, makes every other solar decision easier, because you can see why orientation, shading and the inverter all matter. Here's the whole process in plain English.
The core idea: the photovoltaic effect
A solar panel is a grid of cells made mostly from silicon. When daylight hits a cell, the energy in the light knocks electrons loose, and the cell's design pushes those electrons to flow in one direction. That flow is an electric current. This is the photovoltaic effect, and it's why panels are often called PV panels. The key point: it runs on light, not heat. Panels generate on a bright cold day and keep working under cloud at reduced output, which is why the "too cloudy in the UK" worry is misplaced, as covered in solar panel myths.
From panel to plug: the four steps
- The panels generate DC. The cells produce direct current (DC), the same kind of electricity a battery stores.
- The inverter converts it to AC. Your home and the grid run on alternating current (AC), so an inverter changes the panels' DC into AC at the right voltage.
- Your home uses it first. The AC feeds your consumer unit, and any appliance that's running draws from the panels before it draws from the grid.
- The surplus is exported. Whatever you don't use flows back to the grid, and you're paid for it under the Smart Export Guarantee. When the panels aren't producing enough, you simply draw from the grid as normal.
The parts of a system
| Component | What it does |
|---|---|
| Panels | Convert daylight to DC electricity. A typical panel is about 400 to 450W, so roughly 10 make a 4 kWp system. |
| Inverter | Converts DC to AC. Comes as a single string inverter, per-panel microinverters, or a hybrid that also manages a battery. |
| Mounting | Rails and hooks that fix the panels to the rafters while keeping the roof weatherproof. |
| Generation meter | Records how much the system produces. |
| Battery (optional) | Stores surplus for later instead of exporting it, covered in do I need a battery. |
What changes how much it makes
The same panels produce different amounts depending on a few things: how much daylight your location gets, which way the roof faces, its pitch, the time of year, and any shading. Orientation is unpacked in south vs east-west facing solar panels, and the seasonal swing in solar in a UK winter. None of it changes how the panels work; it changes how much light they have to work with.
Why there are no moving parts
Unlike a wind turbine or a generator, a solar panel has nothing that spins or wears. The conversion happens at the atomic level inside the silicon, which is why panels are so low-maintenance and why they last 25 to 30 years or more, slowly losing only about 0.5% of output a year. The one component that does eventually need replacing is the inverter, typically around years 10 to 15, which is a planned cost rather than a surprise.
The detail most people miss
A grid-tied system shuts down in a power cut, even in daylight, and this surprises people. It's a deliberate safety feature: it stops your panels from feeding electricity into the network while engineers may be working on it. If you want power during an outage, that's a specific battery feature to ask for, not something panels do on their own. The point of solar is cutting your bills every normal day, not acting as a backup generator.
Frequently asked questions
Daylight knocks electrons loose in the panel's silicon cells, creating a direct current. An inverter then converts that into the alternating current your home and the grid use.
Yes, at reduced output. They run on daylight rather than direct sun or heat, so they keep generating under cloud, just less than in bright conditions.
It converts the direct current (DC) the panels produce into alternating current (AC), which is what your home appliances and the grid use. It's the part most likely to need replacing over the system's life.
No. With no daylight there's nothing to convert, so at night you draw from the grid or from a battery if you have one charged.
No. Direct sun gives the most output, but panels also generate from the diffuse light that gets through cloud.