How many solar panels do I need for a power station?

Updated 11 October 2026

It depends on how much energy you use in a day and what season it is. In the UK, the same panels that cover a day's use in summer might cover under half of it in winter. This guide gives the method, then three worked examples.

The method

1. Work out your daily watt-hours. For each device, multiply its watts by the hours you use it each day, then add up. The wattage guide has typical values.
2. Allow for conversion losses. Divide by 0.85, because some energy is lost converting power between the panel, the battery and your device.
3. Divide by what a panel really gives per watt. Multiply the "sun hours" for the season by 0.75 for real-world losses. That is how many watt-hours each watt of panel produces in a day.

The sizer uses 4 sun hours for summer, 2.5 for spring and autumn, and 1 for winter. The UK solar guide shows where those figures come from and why they are cautious.

Worked examples

These use two daily loads from the camping guide: 380 Wh a day (phones, lights and a laptop) and 740 Wh a day (the same plus a small fridge).

For 380 Wh in summer the working is 380 ÷ 0.85 = 447 Wh, then 447 ÷ (4 hours × 0.75) = about 149 W. The same sum in winter is 447 ÷ (1 × 0.75) = about 596 W.

What stands out

• Winter needs about four times the panels. That is rarely practical for a portable setup, which is why winter solar is better thought of as a top-up.
• A fridge is the swing factor. It nearly doubles the panels you need.
• The unit may cap you. A power station can only accept so many watts from its solar input. A 1,160 W array is pointless on a unit that stops at 200 W. See matching panels to your unit.

How long does a refill take?

Using the sizer's figures, a 200 W panel harvests about 600 Wh on a summer day, 375 Wh in spring or autumn, and 150 Wh in winter. To refill a 1,000 Wh battery that is roughly:

These are planning figures. Real days vary with cloud, shade and how well the panel is angled.

Two ways to use solar

• Run it from the sun. Size the panels to match daily use, as above. This works best in summer.
• Use it to extend the battery. Choose a battery for the days you need, and add panels to stretch it. The power sizer works this out if you switch solar on: it sizes the battery for about a day and the panels to refill it.