How solar panels work, and why they work here

Light in, electricity out

A solar panel is a sheet of semiconducting material, almost always silicon, arranged in layers. When light lands on it, the energy knocks electrons loose and they flow in one direction. That flow is direct current, and the effect has a name: photovoltaic. Nothing spins, nothing burns, nothing gets used up.

Direct current is no use to your kettle, so an inverter converts it into alternating current at the voltage and frequency your house and the grid run on. After that it behaves like any other electricity in your consumer unit.

What a British roof actually produces

The UK average is about 998 kWh per kWp installed per year, which is roughly 2.7 peak sun hours a day. A 6.3 kWp system, which is 14 panels on a typical semi, generates around 6,289 kWh a year. Most households use nothing like that much.

Figures assume a south facing roof at optimal pitch with no significant shading. Your free design accounts for your actual orientation, pitch and shading.

Even the lowest figure on that list produces more electricity than a typical home gets through in a year. Where you live changes how fast the system pays back, not whether it works at all. The coverage page shows the generation figure for your postcode area and the local OVO expert who looks after it.

Where the electricity goes, in order

1. Your house takes what it needs first. Every unit you use on site is a unit you have not bought at the 26.11p cap rate.
2. Anything left over charges the battery, if you have one fitted.
3. After that, the surplus flows out to the grid and you get paid for it.
4. When the sun is down and the battery is empty, you import as normal, ideally on a cheap overnight rate.

That order matters more than people expect. Without storage, a lot of a sunny day happens while the house is empty. A battery is what lets you keep the middle of the day for the evening, which is covered properly in our solar and battery strategy guide.

Why a cold, bright day is a good day

Cells lose a little output as they warm up. Datasheets call this the temperature coefficient, and current N-type modules typically sit at around 0.24% to 0.29% of output lost per degree C above the 25C test condition. In practice a crisp bright spring day can out-produce a hazy humid one in July, which surprises almost everyone.

What actually decides your number

• Roof orientation. South is best, but east and west split arrays spread generation across the morning and evening instead of peaking at noon.
• Pitch and shading. Shading costs more output than orientation does, and it is the thing we look hardest at on aerial imagery.
• Usable roof space. Most semi-detached roofs take 10 to 16 panels on one pitch.
• How you use electricity. A house that is empty all day gets far more out of a battery than one that is not.
• Your export rate, because everything you do not use is either income or waste depending on the tariff.

Those five inputs are the whole design. We work through them on the call using satellite and aerial imagery of your roof plus your meter data, and you see the layout on screen as we go. If you want the pricing side first, the solar panel cost guide has the full matrix.

OVO SEG Install Exclusive pays 20p per kWh where OVO installs both solar and battery, or 15p per kWh for solar only. The exclusive rates require you to take your electricity supply from OVO and are subject to system size limits. OVO's standard SEG rate of 4p per kWh is open to customers of any supplier. Rates correct at July 2026 and subject to change.