How many solar panels do I need for my home?
How many panels does an average home need?
Most homes land between 8 and 16 panels. Modern panels are around 400 to 450 watts each, so ten of them make a system of roughly 4kWp. In the North East that generates near 3,400 kWh a year, based on regional output data from MCS installs, which covers close to 90% of what a typical home uses.
For context, an average home uses somewhere around 2,500 to 3,000 kWh of electricity a year (per Ofgem’s typical consumption figures), though a home with an electric car, a heat pump or a large family uses much more. The average domestic system fitted in the UK has been around 4.6kWp (per MCS data), which tells you most homes sit in that 10 to 14 panel range. But an average is not your home, which is why the real number comes from a survey.
How do you size a system from your electricity usage?
Start with how much you actually use, not a generic figure. Dig out your annual kWh from a bill or your online account. The more you use, and the more of it you use during daylight hours, the larger a system can sensibly be.
There is a balance to strike. A system sized to cover a big chunk of your daytime use pays well, because those units are worth roughly 26p each against the grid (per Ofgem). Push the system much larger than your usage and the extra generation gets exported at the lower Smart Export Guarantee rate of around 12 to 15p, which is worth less. If you have an EV or a battery, you can use more of a bigger system yourself, which changes that balance. We work through the battery side in solar panels with or without a battery: do you actually need one?.
How do you size a system from your roof?
Your roof sets the ceiling. Each panel takes up roughly two square metres, so the usable area of your roof decides how many will physically fit once you allow for edges, vents and any obstructions. A typical semi with a clear pitch usually takes 10 to 16 panels.
Orientation and shading then decide how much each panel is worth. A south-facing pitch is ideal. East or west-facing pitches generate roughly 15 to 20% less over a year but are often still worth doing, and some homes split panels across two pitches to fit more in. Shade from a chimney, a dormer or a neighbouring tree can drag down a whole string of panels, so where they go matters as much as how many. We assess all of this on site, as covered in do solar panels damage your roof?.
Should you fill the whole roof with panels?
Not automatically. A bigger array generates more, but if it generates far more than you use, the surplus is exported at the lower SEG rate rather than saving you the higher grid rate. Beyond a certain point you are adding cost for units that earn you 12 to 15p instead of saving you 26p.
Where filling the roof does make sense is when you have the usage to match: an EV to charge, a heat pump, a battery to store the surplus, or a plan to add one of those soon. Then the extra generation has somewhere to go at full value. It is a genuine trade-off between up-front cost, roof space and how much of the output you will actually use, and it is worth working through rather than defaulting to “as many as fit”.
Why an off-the-shelf package is usually the wrong size
The quickest way to end up with the wrong system is to buy a fixed package online before anyone has seen your roof. Those packages are sized to a generic home, not yours, so they tend to be too big, too small, or laid out in a way your roof can’t take.
George puts it plainly: don’t buy a package off the internet before anyone’s seen your roof. The right system is sized from your roof space, orientation and your actual usage, and that is exactly what the free survey is for. A system that fits your roof and your consumption beats a bigger or cheaper one that suits neither.
How to get the right number for your home
The honest answer to “how many panels do I need” is: the number that matches your usage and fits your roof, and that comes from a survey, not a formula. Most homes land in the 8 to 16 range, but where in that range is your question to answer with us.
We size the system from your electricity usage and your roof at a free home survey, and show you the generation and the trade-offs before you commit. Browse the rest of the solar knowledge hub, or book a survey and we will work out the right size for your home.