How do I use powerline adapters?

Sending network over the mains — when they work brilliantly, and the wiring situations where they will not work at all.

Difficulty: beginner
Time: 30 min
Read: 2 min
Safety: caution

Short answer

Plug them directly into wall sockets, never an extension lead. They work well where thick walls block wifi, and poorly where the two sockets are on different circuits or the wiring is old.

Powerline adapters turn your mains wiring into a network cable. Where the house wiring cooperates they are excellent value; where it does not they barely work at all, and the difference is not predictable from the outside.

Safety

Powerline adapters must be plugged directly into a wall socket, never into an extension lead or a surge protector — both filter the signal and some extension leads are not rated for the pass-through. Do not use them where an extension is unavoidable.

What you'll need

Powerline adapter pair
Ethernet cables
A wall socket at each end

Step by step

Buy a pair to start.One for the router, one for the far room. Some sets include a wifi-capable adapter that also creates an access point at the far end.
Plug both directly into wall sockets.Never an extension lead or surge protector. Both filter out the signal, which is the single most common reason people conclude powerline does not work.
Connect the first to the router by ethernet.Short cable from a spare router port to the adapter. Most adapters have a pass-through socket so you do not lose the plug.
Pair them.Usually a button on each, pressed within a couple of minutes of each other. The indicator light tells you when they have found each other.
Check the link quality light.Most have a colour-coded indicator — green good, amber acceptable, red poor. It tells you immediately whether the wiring will cooperate.
Try different sockets if the link is poor.Performance varies substantially socket to socket. Sockets on the same ring perform best; different circuits, or across a consumer unit, perform badly or not at all.
Expect less than the headline speed.Real-world throughput is typically a fraction of the advertised figure, and it depends on the wiring. It only needs to beat the wifi it is replacing.
Accept it will not work in some houses.Old wiring, multiple circuits, or a flat where sockets are on different phases. If the link light is poor in several sockets, a mesh system is the answer instead.

Tips

Powerline is often the best answer for a garden office or a loft room where wifi cannot reach and running a cable is impractical.
The pass-through models are worth the small extra so you do not lose a socket.
Buy from somewhere with a returns policy. Whether they work depends on your wiring and you cannot know until you try.

Questions people ask

Do powerline adapters actually work?

Very well in some houses and barely at all in others, depending on the wiring. Both must be in wall sockets, not extension leads, and both ideally on the same circuit.

Why is my powerline connection slow?

Usually an extension lead, sockets on different circuits, or old wiring. Try several sockets and watch the link quality light.