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 Wednesday, 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.