How Do Solar Panels Work? A Simple Breakdown

Nothing burns and nothing needs refuelling: the panels generate whenever there’s daylight, and the rest of the system decides where the electricity goes.

This guide follows that electricity from your roof to your sockets, then explains what happens in the evening, at night and in a power cut. We design and install solar panels and battery storage for homes and farms across Devon and Cornwall from our base near Okehampton.

How do solar panels work? The short version

Inside a solar cell

A solar cell is a thin slice of semiconductor, most commonly silicon. “Semi” because it conducts electricity better than an insulator but not as well as a metal. When daylight falls on the cell, the silicon absorbs the light’s energy and passes it to electrons in the material. An electrical field built into the cell moves those charges in one direction, and that movement is an electric current. Thin metal contacts, the grid-like lines on the face of the cell, collect it.

Cells are wired together into a panel, and panels into an array. The cells in modern panels look dark blue or black because they’re made to reflect as little light as possible: the less light a cell reflects, the more it can turn into electricity.

Not all the light that reaches a cell becomes electricity. Some is reflected, some passes straight through and some turns into heat. That heat matters, because solar cells generally work best when they’re cool. Higher temperatures reduce the voltage a cell produces, so a bright, cold spring day can be a very good day for solar.

The parts that make it work

Part	What it does
Solar panels	Turn daylight into DC electricity
Mounting system	Holds the panels at a fixed angle on a roof or ground frame, built to cope with wind and rain for decades
Inverter	Converts DC into AC for your home and the grid
Consumer unit	Your fuse box: sends electricity to the circuits in your home
Battery (optional)	Stores surplus electricity to use later
Meter	Records what you import from the grid and what you export to it
Monitoring app	Lets you follow what your system is generating, using and storing

The inverter does more than people expect, and there are different kinds:

Panels and inverters age differently. Solar panels should last 25 years or more, while the inverter is likely to need replacing at least once in that time, so it’s worth knowing which one you have and what its warranty covers.

We fit Sigenergy systems, EcoFlow PowerOcean and Fox ESS inverters and batteries, and we choose them around the job. We’re not loyal to a box. We’re loyal to the right system.

Where the electricity goes: your home, a battery, then the grid

During the day, your home uses solar electricity as it’s generated. The kettle, the washing machine, the fridge: whatever is switched on takes solar power first, and you only draw from the grid for anything the panels can’t cover at that moment.

When the panels make more than you’re using, the surplus has two places to go. If you have a home battery, it charges first. Once the battery is full, or if you don’t have one, the surplus flows out to the grid through your meter.

Electricity you export can earn export payments through the Smart Export Guarantee (SEG). To qualify, your system needs an MCS certificate (MCS is the Microgeneration Certification Scheme) or an equivalent, and a meter that can take half-hourly readings. We’re MCS certified for solar PV and battery storage, and our guide to what solar PV is covers how the SEG works.

Buying a unit of electricity usually costs more than you’re paid for exporting one, so timing matters. The more of your electricity you use while the panels are generating, the more of their output you use directly. On a farm we look at when electricity is needed for milking, refrigeration and ventilation, which is where solar for farms starts; for solar for businesses, it’s about operating hours and daytime demand. If you already have panels and export much of what they make, you can add a battery to an existing system to keep more of it for the evening.

How solar panels work on paper is one thing; how they work on your roof depends on the design.

What happens in the evening, at night and in a power cut

As the light fades, the panels produce less, and at night they produce nothing. From then on:

A power cut is different. Grid-connected systems are built to switch off if the grid goes down. This loss-of-mains protection is part of the rules for connecting generation to the electricity network, known as G98 and G99, and it stops your system feeding electricity into cables that engineers may be working on. It’s tested when the system is commissioned. So panels on their own won’t keep the lights on in a power cut. Some battery systems can supply backup power to the home; backup power is possible where it’s included and suitable, and we’ll tell you plainly whether yours can.

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What affects how well solar panels work

• Direction and tilt. An unshaded, south-facing roof is ideal. East- and west-facing roofs still work; north-facing roofs aren’t recommended.
• Shade. Trees, chimneys and nearby buildings can reduce performance. Microinverters or optimisers can limit the effect where shade can’t be avoided.
• Weather. Panels still generate on cloudy days, at reduced output, and they generate more in bright sunshine.
• Temperature. Cells work best when they’re cool, so the hottest days aren’t automatically the most productive.
• Dirt and debris. In the UK, rain cleans panels tilted at 15 degrees or more. Ground-mounted panels, or panels in dusty areas, may need cleaning now and then.
• Condition. Occasional cleaning and a professional inspection once a year help spot problems early. Our page on regular solar panel maintenance explains what an inspection covers, and our guide to the signs your solar panels aren’t working as they should tells you what to look out for in between.

From survey to switch-on

How solar panels work on paper is one thing; how they work on your roof depends on the design. This is how we approach it:

Our page on solar panels designed around your home explains more about how we work, and you can arrange a site survey when you’re ready.

Understanding how the parts work together makes it easier to judge any quote, including ours.