The storage of solar energy increases consumption and emissions compared to the current method of sending excess energy to the utility grid, according to a study by a team from the Cockrell School of Engineering.

The study, published in the science journal Nature Energy on Jan. 30, acknowledges that solar energy storage saves utility infrastructure costs by reducing power flows in the distribution grid, but it focuses on what many have disregarded — the downside of storing solar energy.

“These findings challenge the conventional notion that energy storage is inherently clean,” said co-author Robert Fares, a Cockrell alumnus and fellow at the U.S. Department of Energy, in a blog post for Scientific American.

The research reports that the typical battery system used today to store solar energy is inefficient, losing energy and increasing annual energy consumption by 324 to 591 kilowatt-hours per household on average. The increase in energy consumption is not the only setback of solar energy storage, Fares said in a blog post.

“With today’s fossil-fuel powered electric grid, the increase in energy consumption also leads to an increase in overall emissions,” Fares said in the post.

The solar energy that is lost in the battery must be compensated for in a different area — the electric grid, which is run by fossil fuels. The researchers calculated that adding storage to solar-powered homes would lead to an increase in carbon dioxide, sulfur dioxide and nitrogen oxide emissions for the average household.

The Solar Energy Industries Association reports the number of homes that have installed solar panels has increased over 1,000 percent since 2004, reaching over 1 million installations in 2016. Currently, almost all solar-powered homes are without on-site storage for their solar energy, according to the Cockrell study.

Study co-author Michael Webber, a Cockrell professor and deputy director of UT’s Energy Institute, said lack of on-site storage isn’t necessarily an issue.

“The good news is that storage isn’t required to make solar panels useful or cost-effective,” Webber said.

Webber and Fares make it clear that using storage with solar panels is still cleaner than not using solar panels at all, but for now, it is better to use solar panels without storage.

“In other words, if a household with solar panels wants to reduce its emissions footprint, adding energy storage is a bad idea,” Fares said in the post. “If we’re not careful, we could actually increase energy consumption and emissions.”