How Much Energy Does That Device Use?

Shahzeen Attari

By Shahzeen Attari

Energy is invisible to the naked eye, but it is a part of every facet of our lives. In a new study, my coauthors and I investigated public perceptions of energy consumption to see how accurate people are in judging how much energy a variety of different activities and devices use.

In an online nationwide survey, participants were asked about the energy used and saved by household and transportation activities, among other behaviors. When asked about the most effective thing they can do to conserve energy in their lives, many Americans think of cutting back on activities (curtailment) rather than investing in home equipment or fuel-efficient transportation (energy efficiency) – this is the opposite of what experts recommend. There may be many reasons why people may think of curtailment rather than energy efficiency, as curtailing ones’ behavior does not involve any upfront costs.

However, the problem with curtailment is that it is hard to make sure people maintain these behavioral changes over a long period of time so that habit formation occurs. As individuals, we have a limited amount of attention and effort we can expend, so energy efficiency investments, if we can afford it, would provide a more effective option. In addition, about 20 percent of our participants stated that the most effective thing they could do was “turn off the lights” — a behavior that may not be very effective to address energy consumption and climate change.

The figure below shows how perceptions of energy consumption map onto actual energy consumed by a variety of different activities and behaviors. Data points that fall on the diagonal line mean that perceptions of energy used or saved are accurate. Data points that fall above the diagonal line are overestimations of energy used or saved, and data that falls below the line are underestimations of energy used or saved.

What we can see from the figure is that people can roughly rank order many devices correctly in terms of how much energy they use, i.e., they know that a dishwasher uses more energy than a laptop computer in one hour. However, they underestimate energy consumption by more than an order of magnitude for large devices such as air conditioners and dishwashers. This may be particularly problematic if coupled with the psychological phenomenon of “single action bias,” which hypothesizes that when individuals are faced with a problem, they may do just one or two things to address it before moving on to the next problem.

In the realm of climate change, individuals may simply make an effort to turn off lights and think they have done their part to address the issue, rather than change behaviors that could save a lot more energy.

Mean perceptions of energy used or saved as a function of actual energy used or saved
for 15 devices and activities. Credit: Attari et al. 2010.

Another interesting finding is that people who are good at math and who have pro-environmental attitudes have more accurate perceptions of energy consumption — yet people who currently incorporate some of these green behaviors in their lives have less accurate perceptions of energy consumption. One reason for this may be that they focus on the behaviors they currently do, and discount other behaviors.

What Can We Do About It?

Accurately understanding how much energy different appliances use is critical to making informed decisions about energy use. Read ‘the short list’ of some effective energy-reducing behaviors you can incorporate in your life. See which ones are easiest for you to implement and try them out. Some of these behaviors may be easier to adopt than you think.

Shahzeen Attari is currently a postdoctoral fellow at The Earth Institute (EI) and Center for Research on Environmental Decisions (CRED) at Columbia University. Her research focuses on the interactions between natural and social systems, in specific human behavior and climate change. Her previous studies have investigated preferences to change individual behavior, perceptions of energy consumption, and motivations for action in social dilemma situations. She holds a Ph.D. in Civil and Environmental Engineering & Engineering and Public Policy from Carnegie Mellon University. She also holds a Bachelors of Science in Engineering Physics from University of Illinois at Urbana-Champaign.

The other authors of the study are Michael DeKay of Ohio State University; and Cliff Davidson and Wändi Bruine de Bruin of Carnegie Mellon University.