Powerline adapters: when they work and when they don't

Plug one in by the router, one in the far room, and the internet travels through the wiring. Sometimes it's brilliant. Sometimes it's worse than Wi-Fi.

Published · 2 min read

In this guide
  1. How they work
  2. When powerline works well
  3. When it disappoints
  4. Powerline with Wi-Fi, or powerline plus an access point
  5. How to test it before you commit
  6. See the room, not just the adapter

Powerline adapters promise a cable without the cable: one plugs into a socket next to the router, another into a socket in the room that needs internet, and the data travels through your home's electrical wiring. Some people swear by them; others return them the same week. Both are right, because the result depends almost entirely on your wiring.

How they work

The first adapter connects to the router with an Ethernet cable and sends the data as a high-frequency signal over the electrical circuit. The second adapter picks it up and turns it back into Ethernet, or into Wi-Fi if it's a model with a built-in access point.

The numbers on the box (600, 1200, 2400) describe a best case on ideal wiring. Real-world speed is usually a fraction of that, and it varies from socket to socket in the same house.

When powerline works well

  • Same electrical circuit, modern wiring. Two sockets on the same circuit in a reasonably recent installation usually give good, stable results.
  • Plugged directly into the wall. Adapters need a direct wall socket, not a power strip.
  • Walls or floors that Wi-Fi can't cross. Concrete, stone or a foil-lined floor stop Wi-Fi but not the wiring. This is where powerline shines.
  • A single far room or an outbuilding on the same supply.

When it disappoints

  • Surge-protected power strips and extension leads. They filter exactly the frequencies powerline uses.
  • Different circuits or phases. Sockets on separate circuits, or on different phases in a three-phase supply, can drop to a fraction of the speed.
  • Old or long wiring, or a path that goes through the fuse box twice.
  • Noisy appliances. Phone chargers, LED drivers, washing machines and some power supplies inject interference. Speed that drops when the washing machine runs is a classic sign.
  • Separate meters. Two flats, or a house and a separately metered annex, usually don't talk to each other.

Powerline with Wi-Fi, or powerline plus an access point

A powerline kit with Wi-Fi in the second adapter is convenient, but that adapter sits at socket height, often behind furniture. If the far room needs good Wi-Fi, a plain powerline adapter feeding a proper access point or wired mesh node, placed high and in the open, usually covers better.

How to test it before you commit

  1. Plug both adapters into sockets in the same room and pair them. That's your best case.
  2. Move the second adapter to the far room, directly into the wall.
  3. Check the connection in the far room, and check it again at a different time of day, with appliances running.

If the far room is good and stable, keep it. If it's good in the morning and poor in the evening, that's wiring noise, and a mesh system or a real cable will be more reliable. See mesh vs extender for the alternatives.

See the room, not just the adapter

The adapter's lights tell you the link is up, not how the Wi-Fi feels at the desk or on the bed. WiFi Heatmap maps the far room before and after adding the adapter, so you can see whether the whole room improved or just the corner where the adapter sits.