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Some musings on Powerline adapters

July 12, 2021

I’ve been using a set of Powerline adapters in my home for several years. I’ve also recommended Powerline to several of my friends and family to solve networking problems in their homes. But they’re not a panacea for all ills. There are some idiosyncrasies which I discuss here. I hope this proves useful to someone.

Note: I’m writing from a UK perspective. While not a qualified electrician, I’m familiar with UK domestic power wiring (240V). I also have a passing acquaintance with European (Portuguese and Danish, 220V) and US (110V) domestic wiring.

What is Powerline?

Powerline (also known as Homeplug) is a technology that uses the mains power cables in your home to carry computer network signals to deliver a network – usually your broadband connection – to places in your home that are otherwise hard to reach. The signals are carried by a high-frequency radio signal over the copper electrical cables in the wall. It’s a technology designed only for domestic networks. It’s not intended for commercial use.

You plug an Ethernet cable from your router, or a point on your existing network, into one Powerline adapter which is plugged into an electric wall power socket. Then you plug a second adapter into a power socket somewhere else in your home and run an Ethernet cable from it to your remote device, which could be a computer, a wireless access point, a TV or a switch to which you connect other computing devices.

Example of the use of Powerline in a home

What types of Powerline adapters are there?

There are different versions for different power systems including US power plugs, UK power plugs, European (Schuko) power plugs and Australian power plugs.

There are versions that occupy a power socket, and there are versions which present a power socket when they’re plugged in; these are known as “pass through” adapters.

A pair of Powerline pass through adapters (UK version)

And there are different speed adapters. The lowest speed, the original versions, were labelled 200 Megabits per second (Mbps). There are 400Mbps, 500Mbps, 600Mbps, 1000Mbps, 1200Mbps and 2000Mbps versions. But in real life I’ve been unable to achieve anything near the claimed maximum speed, so I’d suggest you use a higher speed version than the network you’re trying to connect. I’m using 2000Mbps adapters to carry a 74Mbps network; my neighbour is using much less expensive 600Mbps adapters to carry a 12Mbps network.

And there are lots of manufacturers. In principle, adapters should all inter-operate, but the whole network will drop back to the speed of the slowest adapter, and each manufacturer has slightly different ways of setting up and configuring devices, so it’s generally easiest to use a set of adapters of the same speed all from the same manufacturer if you can. I’ve deployed TP-Link devices and I’m very happy with the build quality, reliability, operation, configuration and performance.

Some adapters offer more than one Ethernet port, so you can use them as a mini switch, connecting more than one device. Some adapters have a WiFi access point built in, so you can instantly set up a new WiFi network without any other devices, or you can use Powerline adapters to extend an existing WiFi network.

This pair of adapters shows one that combines both multiple Ethernet ports and a wireless access point

Decide how you want to use Powerline in your home and then select appropriate devices.

Will Powerline work on any home electric circuit?

To get the best performance you should plug the Powerline adapters directly into a wall socket – extension cables and particularly surge protection devices will attenuate the signal or even filter it out altogether.

Furthermore, it’s recommended that adapters are plugged into the same electrical circuit. Some houses have a separate circuit (ring main in the UK) upstairs from the one downstairs, and some houses which have been extended may have a separate circuit in the new build from the original building. Almost all houses have a separate circuit for sockets in the kitchen.

This doesn’t mean they won’t work across circuits, but they may not. Much seems to depend on how the circuits are protected. Older fused circuits appear to allow Powerline adapters to work across circuits; mini circuit breakers (MCBs) also seem to work, but residual current devices (RCDs) are more problematic. You may need to borrow a pair of adapters from a friend and try them, or make sure you can return the Powerline adapters to your supplier if they don’t work in your home.

Will Powerline work across phases?

In the UK, almost all domestic properties are supplied with single-phase power, but in other countries three-phase is more usual. Powerline adapters aren’t designed to work across phases, so if you’re trying to use them in a three-phase installation you may need to try and rearrange the circuits so the sockets you are trying to connect are both on the same phase. Consult an electrician.

You may be able to use an additional pair of Powerline adapters to bridge phases – I discuss this in more detail later. If you’re in the USA you may be more likely to get them to work across phases – that’s because you are very likely to have a 3-phase 110V installation and a high-power device that bridges two or even three phases. This may allow the Powerline signals to pass. There’s no hard and fast rule about whether they’ll work or not. You’ll just have to try it.

Are there any problems using Powerline?

Because the signal is carried on domestic wiring by high-frequency radio it may interfere with other devices – radio hams have reported Powerline causing interference with their radio equipment Also Powerline itself can be affected by interference from other devices plugged into the power network – I’ve seen reports that microwave ovens cause interference to the Powerline network when they’re operating.

Is my Powerline network secure?

All Powerline adapters are secured with a private key. They are configured by default with a standard key, so out of the box all adapters should work together, even those from different manufacturers.

It’s unlikely that your signal will pass your electric meter. It is also unlikely to pass onto another electrical phase, so it’s very unlikely that your neighbour will be able to connect to your network. But if you live in an apartment block, or in a shared house, then it may be advisable to change the encryption on your network to avoid possible eavesdropping.

All Powerline adapters support this. You can force one of your adapters to generate a new, random, private key and then pair the others with it. Consult your user’s manual on how to do this as each manufacturer, and even different models, may do it differently.

Can I use more than two adapters?

Yes, you can. If you’re using the default configuration you can simply plug in another adapter. If you’ve changed the encryption you will need to pair the new adapter with one of the existing adapters. Again, consult your user manual(s) on how to do that.

My experience is that adding a third and a fourth adapter worked fine, but more than that degraded performance significantly. I currently use three on my home network. They are all on the same electrical circuit, and with broadband speed at the router of 74Mbps I can achieve a 70Mbps connection at each of the remote adapters.

If I can’t get them to work well across electrical circuits, can I bridge them?

You can, but I’ve tried it in my home and my experience suggests that the performance may still be significantly reduced.

You will need to find a socket on one circuit that’s physically close to a socket on the other circuit, plug a Powerline adapter into each of these, and connect them together with an Ethernet cable.

However, to avoid creating a network loop, which will cause problems, you must arrange that the adapters on one circuit are unable to communicate with those on the other circuit via the electric cabling. To do this pair one set of adapters with a new private key (see above and refer to your user manual). You’ll end up with two adapters on one circuit using default encryption, and two adapters on the other circuit, paired together using a new random private key. Then you connect an adapter on one circuit by Ethernet cable to an adapter on the other circuit, creating a bridge.

I believe it is possible to use a specialist connector to bridge circuits at the fuse box/consumer unit, but I’ve only seen devices that do this for 110V US circuits. I’ve not found a UK 240V or a European 220V version.

Is Powerline better than wireless networking?

This depends on the situation, but in my opinion, yes. My networking mantra is, “If you can wire it, wire it”. Connecting networks with physical cables is more reliable, more secure, and usually more performant than wireless.

But if you have multiple electrical circuits and have problems getting Powerline to work effectively then short of running an Ethernet cable round your house – which can be messy and expensive – wireless may be the better solution.

I use both. I prefer Powerline, but I have a room which is on an electrical circuit which won’t work reliably with Powerline from my router no matter how it’s connected. So I’ve installed a wireless repeater to get a decent bandwidth signal to the smart TV in that room.

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