Making appliances more energy efficient won’t have as big an impact on Americans’ pocketbooks as the government says, according to a new report from two environmental groups.

The study, released by the American Council for an Energy-Efficient Economy and the Appliance Standards Awareness Project, says that contrary to what the U.S. Department of Energy predicted, prices of most appliances dropped as regulations tightened efficiency standards.

"Even when prices have gone up some, the increase is far lower than DOE estimated,” said Steven Nadel, executive director of the council and lead author of the report.

The study looks at nine appliance standards that took affect between 1998 and 2010. It says the Energy Department overestimated the price impact every time. The department predicted an average list price increase of $148; in reality, prices dropped about $12 on each appliance.

"Energy efficiency standards are proving to be an economic powerhouse, driving even more consumer savings than we realized," said report co-author and ASAP Executive Director Andrew deLaski. "Predicting price changes in dynamic markets is difficult and, fortunately, DOE has already taken some steps to improve their estimates. Our analysis shows that, even accounting for recent estimation technique improvements, DOE's price predictions are still too high."