Backup power, sized from the numbers up

Why we built this

Buying backup power usually means wading through VA ratings, watt-hours and runtime graphs that don't map onto real life. Will it run the fridge overnight? Keep the router going so the landline works? Give the server long enough to shut down? The spec sheet rarely says.

So we built the Power Sizer: pick what must stay on and it does the maths, then shows which products genuinely fit — and which ones don't, and why. Every product page carries the same "Can it run?" panel, so you can compare like with like.

How we estimate runtimes

• We use typical UK wattages for common devices, and average draw for things like fridges that cycle on and off.
• For lithium power stations we assume about 85% of rated capacity reaches your devices.
• For traditional lead-acid UPS units we model how capacity drops at higher loads, which is why a small UPS lasts minutes, not hours, under a desktop PC.
• They're estimates. Your devices, battery age and temperature all make a difference, so we always link to the maker's own figures.

How we choose products

• We organise by situation first — desk, home or off-grid — and spec sheet second.
• We favour established brands with solid warranties and UK support.
• Rankings are never for sale. Some links are affiliate links, and that is disclosed.