Researchers have invoked the self-licensing effect to explain why consumers who opt for energy-efficient products increase their energy usage so as to offset any potential gains. Energy economist Lucas Davis published a study showing that after getting high-efficiency washers, consumers increased clothes washing by nearly 6 percent.[14] Other studies have shown that people leave energy-efficient lights on longer than conventional lights, and that many people who make their homes more energy efficient turn their heating up and ultimately see no reduction in energy costs.[7]