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.

How many solar panels does a house need?

How many solar panels for a 4 bedroom house? Most four bedroom homes use 4,000 to 4,500 kWh a year, which points at 11 to 13 panels and a system of around 5kW, as long as the roof has the space.

How many solar panels to run a heat pump?

An air source heat pump typically adds 3,000 to 4,000 kWh a year to a home’s electricity use, so covering it on paper means roughly seven to nine extra panels. In practice solar generates least in winter, when a heat pump works hardest, so a battery and a cheaper overnight tariff do more of the work in the colder months. Our heat pumps page explains how the two work together.

How many solar panels can I fit?

Each panel needs roughly two square metres, so divide your usable roof area by two and leave space around the edges. Systems up to 3.68kW per phase connect under the G98 process, with the network operator notified after installation. Anything larger needs G99 approval from SP Energy Networks first, and we handle that paperwork for you.

Is 4 solar panels enough?

Four panels make a system of about 1.6 to 1.8kW, which generates roughly 1,500 kWh a year in this region. That trims a small household’s daytime usage, but it falls well short of the 2,900 to 3,200 kWh a typical North Wales home uses.