Using less energy saves money and lowers greenhouse gas . And various studies have looked at ways to get to use less energy. Now there's evidence that people in such a study use less energy…because they're in a study. The general is called the effect: study subjects change their behavior because they're being observed. So collaborated with a utility to test for the Hawthorne effect in electricity use. They almost 5,600 randomly selected households. Half received a postcard saying that their energy use would be monitored for a month for research purposes. They also got four follow-up reminder postcards over the month. They received no other information, instructions or incentives. The control group monitored for the study got no notifications. That group continued using the same amount of electricity. But the families being tracked reduced energy use 2.7 percent. And when the study period ended, their energy use shot back up. The report is in the of the National Academy of Sciences. Clearly, mindful consumers can find ways to easily lower their energy consumption. Perhaps policy makers can find a way to use the Hawthorne effect to everyone's advantage.