There is even a name for it: the Snackwell Effect.
Just as dieters might binge on Snackwell's low-calorie cookies, people who buy energy-efficient items for their homes sabotage their efforts to save power -- often by using the appliances more heavily, studies have shown.
A marketing survey to be released today showed that one-third of respondents who made energy-efficiency efforts at home saw no decrease in their energy bills, and a 2008 study by University of Michigan economist Lucas Davis found that people given energy-efficient washing machines washed more clothes.
"It could be that by doing something virtuous, it gives you license to do something indulgent somewhere else," says Portland State University's Loren Lutzenhiser, who studies energy consumption.
People who install efficient lights lose 5-12 percent of the expected energy savings by leaving them on longer, said Karen Ehrhardt-Martinez of the non-profit American Council for an Energy Efficient Economy. People who buy an efficient furnace lose 10-30 percent of their savings, probably from raising the thermostat, she said.
"It doesn't mean energy efficiency is a waste of time," says Sussex University's Steve Sorrell, who wrote a 2007 report for the federally funded UK Energy Research Centre on the phenomenon, which economists call the takeback effect. It does mean that "standards on efficiency will not be sufficient by themselves."
The takeback effect could cut the energy savings from measures being championed in Washington. The $787 billion stimulus package signed by Obama last month includes $5 billion for weatherization programs and $300 million in rebates for energy-efficient products
In a new survey of 500 Americans by the Shelton Group, one-third of respondents reported that they hadn't seen the expected cuts in their energy bill after investing in energy-efficiency measures such as weatherstripping. Alan King of Morgantown, W.Va., for example, says he and his wife purchased energy-efficient appliances but their electric bill has changed little.
King confesses that sometimes his wife will wash just one piece of clothing in their high-efficiency washer, which she would not have done before.
One solution: Devices that tell people how much electricity they use hour-by-hour, so they know the power consumed by a particular appliance.
"People don't really know what they're using," says Lynda Ziegler of Southern California Edison. "At least on a cookie label there's the number of calories."