Powerline adapters: Home networking without rewiring

The concrete and plaster in his Rathdrum, Idaho, house blocks Wi-Fi signals. But computer consultant Marc Schoenberg found a way to network the six devices in his house without stringing Ethernet cables: He uses powerline adapters.

"I use them with wireless access points to fill in the various dead spots around the house," Schoenberg said. "Or when the weather is nice, I use them to provide connectivity outside so I can lie in a hammock and, ummm, work."

Indeed, the average U.S. house has about 40 power outlets, and with powerline adapters, any of them can be turned into a data port. No additional wiring is necessary.

Powerline adapters were previously limited by interference from the electrical noise generated by appliances and household gadgets using the same circuit, but the latest generation appears to have largely overcome that problem. Also, the adapters offer a theoretical speed of about 200Mbit/sec., which is enough to handle digital video signals, even when actual throughput is less than half the theoretical speed (as is common with Ethernet).

But do they work? Lamont Wood puts powerline adapters through their paces.

There are three competing (and largely incompatible) technologies on the market: the HomePlug AV standard from the HomePlug Powerline Alliance, the Universal Powerline Association (UPA) standard, and Panasonic's High-Definition Powerline Communications (HD-PLC) specification.

Besides somewhat comparable speed, all of them offer configurable encryption, both to prevent eavesdropping and to avoid crosstalk with other networks of powerline adapters that might reside on the same circuit. (All powerline adapters downstream from the power company's transformer can hear one another.) If they come with any software at all, it is intended primarily to set the encryption key. They support at least 16 units on a circuit, with the units automatically configuring themselves into a network.

Powerline adapter from ActionTec Electronics Inc., showing the power prongs and the Ethernet port.

With all three technologies, the powerline adapters are a little bigger than a cell phone. Each has prongs for a power outlet as part of the unit or at the end of an extension line, and each also has an Ethernet port. The user plugs the unit into a power outlet and attaches one end of an Ethernet cable to the Ethernet port and the other end of that cable to a computing device.

After the user does the same with a second adapter and a second computing device (typically a router), the two devices are connected as if via an Ethernet cable. There are usually indicator lights on the adapter to show that it's functioning.