WASHINGTON How can I persuade you to conserve energy? I could remind you that using less power saves money and helps the environment, but you won’t listen. Studies have proven that appeals to cost and conservation have no impact on people’s energy consumption.

But what if I told you everyone in your neighborhood is reducing their energy consumption – except you? Would competition and a little fear of judgment convince you to switch off your air conditioner?

That’s the theory driving Opower, a company that has helped millions of people lower their energy bills. Rather than sell or produce energy, it makes software – software that is changing the way Americans consume energy by setting them in a contest against their neighbors. In the process, Opower has discovered that when it comes to energy efficiency, conscientiousness doesn’t inspire nearly as much change as competition (and a little judgment).

At the heart of Opower’s software is the behavioral nudge – a gentle push toward the right decision. Perhaps the most infamous such example was implemented in the Amsterdam airport, where painting flies on urinals reduced spillage by 80 percent. (If you give a man a target, he can’t help but aim.) In the same vein, Google’s cafeteria is brimming with nudges toward a healthy diet: Healthy foods are coded in green, guilty pleasures in red; plate sizes are smaller-than-average; and the most indulgent desserts are banished to a far corner of the room. Similarly inspired fitness apps encourage you to out-exercise your friends. But using behavioral psychology to encourage energy efficiency has been more difficult, in part because while almost everyone wants to save energy (for both environmental and financial reasons), the resolve to do so wavers once the thermostat climbs. Turning intent into action requires a special kind of push.

Robert B. Cialdini, a well-regarded researcher and author of “Influence: The Psychology of Persuasion,” began thinking about that in 2001. When a summer heat wave in California led to blackouts, he decided to investigate why the state seemed unable to prevent the grid-frying overuse. The big problem: While 90 percent of Californians ranked energy conservation as “very” or “extremely” important, and 98 percent claimed to “try to conserve energy,” virtually no one was taking the necessary steps in their own homes.

To learn why, Cialdini and his team placed door hangers on thousands of homes near San Diego. Three of these hangers provided standard rationales for energy efficiency: saving money, protecting the environment and helping future generations. A fourth merely listed strategies for saving energy. These hangers each had only a negligible effect on energy consumption.

But another hanger tried a different tack, reporting that a certain percentage of the neighbors were using fans instead of air conditioning. It was, in essence, altruistic peer pressure – and it worked. The houses that received that hanger showed a 6 percent average drop in consumption, massive in the world of energy efficiency (and more than three times as much as the other homes targeted for messaging).

That study buttresses Opower’s strategy. Since its founding in 2007, the company has been teaming with energy producers to monitor customers’ energy consumption. Opower processes information from companies, then produces detailed energy consumption reports sent to each household, like when they use the most energy and what appliances are most wasteful. The reports are mailed to homes on paper – a seemingly counterintuitive medium for a company whose mission is cutting waste. Yet Opower has discovered that virtually no one will go out of their way to read an online energy report or take the time to parse its often-dense details.

In addition to giving you feedback on your energy use, the report includes a bar graph that compares your own energy consumption with your community’s average and that of your community’s most energy efficient households – all of which can be helpful. But the real key is one last box: a grade assessing your energy consumption. You receive two smiley faces for great conservation (that is, using less than 80 percent of what your neighbors do), one for good (using less than most of your neighbors do), none for bad (using more than most of your neighbors). As soon as customers received their first reports and saw the smiley face box, they began increasing their energy efficiency.