How Many Solar Panels Do I Need?

The number of panels you need depends on two things: how much electricity you use, and how much roof you have. Everything else is arithmetic. Here is how we size systems when installing solar panels across North Wales, with worked examples from the region’s housing stock.

From usage to panels, in three steps

Each panel occupies roughly two square metres, so a 4kW system needs about 18 to 20 square metres of suitable roof.

Worked examples from North Wales housing

Do not forget orientation and shading

A south-facing roof is ideal but not required. East-west arrays split across two roof faces generate well, spreading production across morning and evening when you actually use power. Shading from chimneys, dormers or trees matters more than direction, which is why panel count alone never tells the whole story.

Should the count include a battery?

A battery does not change how many panels you need, but it changes how much of their output you keep, storing daytime generation for the evening. If you are sizing a new system, it is worth deciding on the battery at the same time so the right inverter goes in from day one. If you already have panels, retrofitting is covered by our battery retrofit service. What the system costs is covered in our North Wales cost guide.