To curb the climate crisis, experts have stressed the importance of transforming our energy system, from making buildings and household products more energy efficient to moving toward renewable energy sources. But how those changes will interact with human energy use—and human nature—will also have an effect on their success. A recent study stresses the importance of how our behaviors and lifestyles can be unconsciously changed by sustainable innovations, to the point of potentially undermining them.
For the study, published recently in the journal Global Environmental Change, University of Utah researchers set out to analyze two main climate change solutions: improving energy efficiency, and transitioning to renewables, two of the most common and broadly implemented emissions-reduction strategies. “I thought, ‘If the world thinks that these are the two best solutions right now, why don’t we see between these two which one is best?” says Lazarus Adua, an assistant professor of sociology at the University of Utah and lead author of the study.
Researchers compared each state’s CO2 emissions, based on Department of Energy data, with their investment in those two solutions between 2009 and 2016. For energy-efficiency investments, they used the American Council on an Energy-Efficient Economy, which scores states based on their policy initiatives for improving efficiency in buildings and homes, and also each state’s economic output per unit of energy consumed (found by dividing a state’s economic output by its energy input) to calculate how efficient the state’s GDP is overall. For renewable investments, they calculated how much of each state’s total energy consumption comes from renewable sources.
The goal was to find which solution was associated with the biggest drop in emissions, and his team looked at each solution’s impact across four sectors: residential, commercial, industrial, and transportation. The good news is that both policies work: transitioning to renewables and increasing energy efficiency were associated with reducing CO2 emissions when looking across all those sectors—and in fact, there was no statistically significant difference between them.
The study found that a 1% improvement in economic output per unit of energy—making the entire state’s economy more energy efficient—generated about 0.61% reduction in CO2 emissions. “If they use less energy to produce every output, it means they are more efficient,” Adua says. Moving to renewables also had an impact overall. A 1% investment in renewables generated a .7% decrease in total energy-related CO2 emissions, when looking at all sectors.
But a surprise came when they looked at specific sectors and more granular policies. In the residential sector, the researchers found the reverse: A 1% increase in renewable energy was associated with an about 0.36% increase in residential sector CO2 emissions from energy consumption. Similarly, policies focused on helping consumers improve their own energy efficiency had no effect on emissions. “This measure is about state governments working with utilities and providing what we call ‘energy-efficiency programming,’ and part of it is looking at how to get households and buildings to minimize their energy consumption,” Adua says.
The expectation was that both these solutions would reduce emissions, but they didn’t—and that suggested to Adua that a phenomenon called the “rebound effect” was in play. “It isn’t that those policies were not working, technically, as they’re supposed to work. It actually means that they may have worked so well, there is a rebound in consumption as a result,” he says. “And the rebounding [is] driven by human behavior.”
Evidence of the rebound effect—which basically says that when things become more efficient, people tend to use them more, overriding the benefits of efficiency—has been documented multiple times, with all sorts of environmental behaviors. One study found that fuel-efficient cars encourage us to drive more. The first documentation dates back to 1865, when an English economist detailed how advances in steam-energy efficiency actually increased coal consumption in Britain, rather than decreasing it. We see it with carbon offsets, where their use has inadvertently given people or corporations license to pollute more. Adua offers another example outside of the environment: If you go to the gym, and then treat yourself to desert, you might have just ingested more calories than you burned off during your workout.
If someone sees their energy bills going down because that energy now comes from renewables, or because their homes are more efficient, they may, not even intentionally, start to use more energy—leaving lights on or running appliances more often because, in the back of their head, they know those things are being powered in a (more) environmentally friendly way. The rebound effect seems to happen when people see the benefits of these solutions directly. Their behaviors tend to go in the opposite way—consuming even more energy now that they know their homes are being powered off renewables.
This isn’t a reason to stop these policies, Adua says. But it is a reminder that when implementing such policies, like the Biden Administration’s program to retrofit homes to be more energy efficient, officials also need to think about how to avoid the same rebound effect. “It is not the policy that is not working. It is not efficiency that is not working. It is generally the way that human behaviors interface with them,” Adua says. “Even though these things work, we may have to consider lifestyle [changes] too.”