What's The Limit of a 13A Socket?

Aug 07, 2023

If your home working setup is anything like most of the team at Tech Advisor, it will involve a multi-socket extension lead connected to a mains socket in the wall with a PC, monitor, speakers, printer and possibly other devices all plugged into it.

And you might well wonder if attaching so many devices to one 13A socket will overload it.

Fortunately, it’s easy to work out – or see – if your devices are drawing too much power.

There is no limit to how many devices you can power from a single socket. What matters is how much power they all draw.

If you have – or are willing to buy – a power meter you can see exactly what the number is by plugging it into the socket, and plugging your device(s) into that. They’re not too expensive: you can pick up something like the Energenie power meter for under £20.

It’s unlikely to show amps, but instead how many Watts are being drawn.

Jim Martin / Foundry

There’s a simple formula to work out how many Watts is the maximum: Amps * Volts = Watts.

Since the UK uses 230 Volts (+/- 10 percent) and the socket has a limit of 13 Amps, the calculation is as follows:

13 * 230 = 2990W

That means you can connect as many devices as you like so long as their combined power is 2990W or less. That’s the limit of a single UK 13A mains socket without overloading it.

But what if you don’t have a power meter? You can look for a sticker on each device as some will tell your how many Watts they use, but you could also check the manufacturer’s specifications in the product manual or online.

For PCs, you’ll easily find out the rating of its power supply by looking on a sticker on the side, such as 550W. However, this isn’t the amount of power the PC will use: it’s the maximum wattage the power supply is capable of delivering to the PC components.

In general use, a PC will consume much less than its PSU’s maximum rating. In our experience PC’s typically use between 80 and 400W.

Laptops use less power: typically under 100W when charging.

LED monitors and inkjet printers consume roughly 20-50W, and speakers generally less than this. Laser printers only use hundreds of watts when they’re printing, and when idle hardly anything.

So, it’s obvious you can run at least two PCs safely from a single mains socket.

Other devices might user more or less power. A modern 55in TV might draw around 150W, but a heater or kettle could well use the full 3000W on its own.

If you want to do your own calculations, simply add up the maximum power consumption (in watts) of each device and make sure the total doesn’t exceed 3000W.

You can save money by cutting your electricity usage using some of these tech gadgets and find out how much it costs to charge your devices.

Yes. However, you should make sure that the cable isn’t coiled or covered.

Current flowing in a cable generates heat, and this heat needs to be dissipated. When a cable is coiled and the current is near the maximum the cable can handle, the heat generated can melt the insulation and cause a fire when the copper cables touch each other.

This is also why you shouldn’t cover cables under carpets, rugs or anything else. Here’s what can happen when a coiled extension lead is used to power appliances that use a lot of it:

PCs and peripherals use a relatively small amount of power and therefore a coiled or covered power cable shouldn’t pose a major risk, but it’s still best to avoid that risk.

You’ll find more electrical safety advice on the Electrical Safety First website.

Jim has been testing and reviewing products for over 20 years. His main beats include VPN services and antivirus. He also covers smart home tech, mesh Wi-Fi and electric bikes.