In the UK, solar panels often produce around 800kWh to 1,000kWh of electricity each year for every 1kWp installed. kWp measures the total peak capacity of your solar array.
However, they don’t produce exactly the same amount of electricity on every home. There are far too many factors involved to give a precise figure. Your roof orientation, available space, shading, location, the size of your system, and so on all affect how much energy solar panels produce, as well as how sunny it is.
On this page, our team has put together the information you might need if you’re thinking about getting solar panels, or are wondering if your array is working as efficiently as it should.
How do solar panels produce electricity
Solar panels are made up of dozens of small photovoltaic (PV) cells, usually made from silicon. When sunlight hits these cells, it knocks electrons loose from their atoms, creating a flow of electricity. This is called the photovoltaic effect, and it’s been used commercially for decades.
The electricity generated at this point is direct current (DC), but most UK homes run on alternating current (AC). That’s why every solar panel system needs an inverter. This device sits between your panels and your home’s electrics, converting the DC power from your panels into usable AC power for your appliances, lights and sockets.
You don’t need scorching sunshine for this process to work. Solar panels generate electricity from daylight, not heat, so they’ll still produce power on cloudy days, just at a reduced rate. Direct sunlight simply means more energy hitting the cells, so you’ll generate more electricity on clear, bright days than on overcast ones.
How much electricity might my solar panels generate?
Here’s a rough guide to annual generation for a reasonably well-positioned, largely unshaded UK roof:
- 3kWp system: 2,400kWh to 3,000kWh
- 5kWp system: 2,800kWh to 3,500kWh
- 4kWp system: 3,200kWh to 4,000kWh
- 5kWp system: 4,000kWh to 5,000kWh
In Britain, a typical home solar installation is around 3.5kWp. This usually involves six to 12 panels and around 10 to 20 square metres of roof space.
Of course, these figures are estimates only. They aren’t a guarantee. Your solar panels could produce less energy, or they could produce more.
Will solar panels cover all my electricity use?
Probably not, no. Certainly not all the time.
Your panels produce electricity during daylight hours, with the highest output usually around the middle of the day. Your home uses solar electricity first. Unless you have a solar battery or another way to use the surplus, such as charging an EV, any unused electricity is exported to the grid.
If your system is eligible for a Smart Export Guarantee (SEG) tariff, you can be paid for each kWh of electricity you export. However, using your own solar electricity usually delivers the greatest saving because you avoid having to buy that electricity from the grid.
That’s where solar batteries come in. A battery helps you keep some daytime solar electricity for the evening. It won’t make your home fully independent from the grid, especially during winter. It simply helps you use more of the electricity your panels already produce, which can lead to more savings and more control over your electricity use.
How do solar storage batteries work?
A solar storage battery stores the excess electricity your panels generate but don’t use straight away. Without one, any spare power gets sent back to the grid, often for a lower rate than you’d pay to buy the same amount of electricity back later.
During the day, your panels will often generate more power than your home needs, especially if you’re out at work or the kids are at school. Rather than exporting all that excess, a battery captures it and holds onto it until you need it, such as in the evening when your energy use goes up.
Most home batteries use lithium-ion technology, similar to what you’d find in an EV or a laptop. They charge up when there’s surplus solar power available, then discharge that stored energy into your home once your panels stop producing, such as overnight or on darker winter days. Paired well with your usage habits, a battery can significantly reduce how much electricity you need to buy from your supplier.
What affects how much electricity my system produces?
The biggest factor is the roof itself. A south-facing roof with little shade usually gives the highest annual output. East- and west-facing roofs still work well, although they often generate around 15% to 20% less electricity than a south-facing solar array. They may also suit homes that use more electricity in the morning or late afternoon.
Shade from trees, chimneys, nearby buildings, dormers and roof features will also reduce your output. In some cases, panel optimisers help limit the impact of shade on the rest of the system.
Finally, there’s the obvious. Solar output is highly seasonal. Your panels will generate far more electricity during the longer, brighter days of summer than they will in winter, and output will also be lower on overcast days. For that reason, annual generation is a more useful measure than a flat daily average, as the electricity your system produces won’t be spread evenly across the year.
On that note, do remember that solar panels generate electricity from sunlight, rather than heat, although the two often go hand in hand.
How should all this factor into my solar panel quote?
If you’re thinking about getting solar panels, don’t focus only on the headline price or the number of panels. Ask for an annual generation estimate. Your installer should be able to put together a custom estimate for you that accounts for the system’s size, your roof’s direction and pitch, shading and expected electricity use in your home. If relevant, they may also factor in battery storage, EV charging, heat pumps and other future electrical upgrades.
At Electrical Innovations, we only recommend systems tailored to the way you live. We’ll help you navigate the sometimes-overwhelming world of smart tariffs, chargers and battery storage solutions, with clear quotes and dedicated personal service.
So, if you live in or near Derby, elsewhere in the Midlands, or within our service area, contact Electrical Innovations for a no-obligation chat about how much solar energy your home could generate, and whether solar would be a worthwhile investment for you.
