By STEVE LOHR

When computers are watching them, people use less electricity.

Giving people the means to closely monitor and adjust their electricity use lowers their monthly bills and could significantly reduce the need to build new power plants, according to a yearlong government study.
The results of the research project by the Pacific Northwest National Laboratory of the Energy Department, released in January, suggest that if households have digital tools to set temperature and price preferences, the peak loads on utility grids could be trimmed by up to 15 percent a year.
Over a 20-year period, this could save $70 billion on spending for power plants and infrastructure, and avoid the need to build the equivalent of 30 large coal-fired plants, say scientists at the federal laboratory.
The demonstration project was as much a test of consumer behavior as it was of new technology.
Scientists wanted to find out if the ability to monitor consumption constantly would cause people to save energy - just as studies have shown that people walk more if they wear pedometers to count their steps.
In the Olympic Peninsula, west of Seattle, 112 homes were equipped with digital thermostats, and computer controllers were attached to water heaters and clothes dryers. These controls were connected to the Internet.
The homeowners could go to a Web site to set their ideal home temperature and how many degrees they were willing to have that temperature move above or below the target.
They also indicated their level of tolerance for fluctuating electricity prices.
In effect, the homeowners were asked to decide the trade-off they wanted to make between cost savings and comfort.
The households, it turned out, soon became active participants in managing the load on the utility grid and their own bills.
“I was astounded at times at the response we got from customers, said Robert Pratt, a staff scientist at the Pacific Northwest National Laboratory and the program director for the demonstration project.
“It shows that if you give people simple tools and an incentive, they will do this. “And each household, Mr. Pratt added, “doesn’t have to do a lot, but if something like this can be scaled up, the savings in investments you don’t have to make will be huge, and consumers and the environment will benefit.
After some testing with households, the scientists decided not to put a lot of numbers and constant pricing information in front of consumers.
On the Web site, the consumers were presented with graphic icons to set and adjust.
Behind the fairly simple consumer settings was a sophisticated live marketplace .
Every five minutes, the households and local utilities were buying and selling electricity, with prices constantly fluctuating by tiny amounts as supply and demand on the grid changed.
The households in the demonstration project on average saved 10 percent on their monthly utility bills.
The research project was done with an eye toward guiding policy on energy- saving programs.
Efficiency programs promise to curb America’s fuel bill and reduce damage to the environment, if consumers can be persuaded to use energy more intelligently.
Still, a big question among economists and energy experts is how to tailor incentives to prompt changes in energy consumption.
Some experts say the only way to make real progress in household energy efficiency is with sizable subsidies and mandated product standards.