Study finds storing solar power increases energy consumption and emissions

February 01, 2017 // By Nick Flaherty
Storing solar energy for nighttime use with battery packs such as Tesla's Powerpack actually increases both energy consumption and emissions compared with sending excess solar energy directly to the utility grid, finds researchers.

Homes with solar panels do not require on-site storage to reap the biggest economic and environmental benefits of solar energy, says the study from the Cockrell School of Engineering at The University of Texas at Austin.

According to the Solar Energy Industry Association, the number of rooftop solar installations grew to more than 1 million U.S. households in 2016, but few have on-site storage to hold their solar energy for later use in the home.

"The good news is that storage isn't required to make solar panels useful or cost-effective," said Michael Webber, a professor in the Department of Mechanical Engineering and deputy director of UT Austin's Energy Institute. "This also counters the prevailing myth that storage is needed to integrate distributed solar power just because it doesn't produce energy at night."

The study looked at electricity data from almost 100 Texas households that are part of a smart grid test bed managed by Pecan Street, a renewable energy and smart technology company housed at UT Austin. They found that storing solar energy for nighttime use increases a household's annual energy consumption -- in comparison with using solar panels without storage -- because storage consumes some energy every time it charges and discharges. The researchers estimated that adding energy storage to a household with solar panels increases its annual energy consumption by about 324 to 591 kilowatt-hours.

"I expected that storage would lead to an increase in energy consumption," said Robert Fares, a fellow at the US Department of Energywho also worked on the study. "But I was surprised that the increase could be so significant -- about an 8 to 14 percent increase on average over the year."

The researchers also found that adding storage indirectly increases overall emissions of carbon dioxide, sulfur dioxide and nitrogen dioxide based on the electricity grid using fossil fuels. he increase in emissions is primarily due to the increase in energy consumption required to account for