In Anchorage, Alaska this week mayor (and U.S. Senator elect) Mark Begich showed off street lights that can be dimmed and turned up remotely to conserve power.

But one of the more interesting aspects of the demonstration is what's inside the network.

Anchorage's streetlights will be controlled through power line networking, a technology that often gets overshadowed by wireless technologies such as ZigBee and WiFi in smart metering discussions. Power-line networking can costs substantially more, say analysts, but in certain applications it makes sense because of improved performance.

In the Anchorage example, radio frequency chips couldn't be used because of potential for signal interference, according to E chelon. In a "Kitchen of the Future" created recently by McDonald's, the burger giant selected power-line networking to link together appliances over a wires option.

"The reason it is power-line based is that RF (radio frequency) doesn't work," said Steve Nguyen, director of corporate marketing for Echelon. "You get degradation in the signal."

Although not as prevalent in smart-metering trials in the U.S., power line is popular in Europe, he said. Over 27 million homes in Italy have smart meters hooked up to power-line networks. Enel provided the meters and Echelon did the power line networking. There's close to another 1.5 million smart meters scattered through the rest of Europe. The company is also working on a 58,000 smart meter project in Ohio.

Last month, IBM kicked off a project with International Broadband Electric Communications to bring broadband to close to 340,000 homes in rural sections of the southeast in the U.S. IBM also has a strong and growing practice in energy management and smart grid.

The primary advantage of power line arises from the fact that it's not wireless. Power line networking chips (and the algorithms that go with them) essentially allow communication signals to travel on the same wires that go to the lights. As a result, rapid, finely tuned commands can be shuttled from a utility without worries that other radios or environmental disturbances will hamper it. And fine-tuning the commands is essential in many applications.

In the Anchorage project, for instance, the streetlights can be dimmed slightly when there's substantial amounts of snow present because the reflection off the snow provides some illumination. Lights can also be dimmed and increased as traffic swells and fades.

Applications can also be added on top of light control. In Quebec, the government is collecting data from motion sensors and LED lights linked into a power-line network to see if the system can alert safety teams about the existence of recent accidents or pinpointing their location. Oslo is trying to meld a pedestrian safety application into its power-line streetlight network. The Norwegian city has seen power consumption for streetlights decline by 50 percent and maintenance decline by 30 percent.

Streetlights rigged with power lines can keep track of city buses or trains: a small LCD screen can then precisely pinpoint when the next one arrives.

So why isn't the debate over? The power line "powers that be" have been trying to iron out their own technical snags and cost issues to deal for the better part of the decade. A persistent complaint is that power line interferes with ham radios and emergency equipment. Using power lines to deliver Internet or TV into U.S. homes has perennially lagged way behind DSL. (Interestingly, in the Italy example, the smart meters speak to a data concentrator over power line and the data concentrator speaks to the utility via standard IP wireless networks.)

Oops, and then there is price. Adding power-line communications capabilities into a light bulb or a washer can cost $50, said Jonathan Gaw, a research manager at IDC.

"That is way too much to put into every lamp in your house," he said.

Similar capabilities with ZigBee run about $15, Gaw said. ZigBee offers far less bandwidth, but in houses that works fine. Here's a sample of what the conversation will be inside a smart home. Meter: "Peak power prices hit. Turn down by 25 percent." Lamp: "OK."

Wireless is also more practical in some applications, such as water metering where soil moisture sensors may be powered by batteries.

Which of these ultimately gets used will likely be determined in the beta tests conducted by utilities over the next several years.