Workers install portions of an 8.5 megawatt-hour battery system at Fort Carson, Colorado. Credit: Scott Clark / U.S. Army Corps of Engineers

Energy storage has clear benefits, but its impact on greenhouse gas emissions isn’t fully clear.

Massachusetts’ latest energy efficiency plan is being hailed as a national model, but one expert notes that whether its energy storage provision will reduce carbon emissions is still an open question.

In January, the Massachusetts Department of Public Utilities approved the state’s latest three-year energy efficiency plan, which for the first time allows efficiency funds to be used for energy storage projects that reduce peak demand, the highest demand placed on the grid in a given day.

Batteries, however, are inherently inefficient. In the process of storing and then releasing power, some electricity is lost. Therefore, for every kilowatt-hour of energy drawn from a battery, more power — and perhaps more emissions — must be generated in the first place.

“Storage won’t help the consumers or the state of Massachusetts use less energy,” said Eric Hittinger, an assistant professor of public policy at the University of Rochester with a focus on electricity production. “I wouldn’t look to storage to save any emissions.”

The Massachusetts plan includes aggressive fuel savings targets, incentives for homeowners to adopt more efficient heating, and plans to invest in research into cleaner fuels.

Typically, energy efficiency refers to strategies that use less electricity — and produce less emissions — to achieve essentially the same results: the same warm homes, the same clean dishes, the same dry clothes. However, reducing peak demand is not about lowering the total amount of energy used, but about shifting when it is used. To include peak demand reduction under the banner of efficiency, therefore, requires an expansion of the traditional definition.

“It’s a paradigm shift,” said Todd Olinsky-Paul, project director for Vermont-based nonprofit the Clean Energy Group and the author of a recent report arguing Massachusetts’ approach should be a model for other states.

Batteries are increasingly part of the conversation about lowering the peak. They can release their stored energy at peak times, reducing the demand placed on the grid. Lower peak demand enough, the thinking goes, and you can decrease the need to run the dirtiest, most expensive plants.

Storage can also help make the grid more reliable, supporters argue; if very high demand threatens to trigger power outages, batteries can be discharged to ease the burden on the grid. If storms damage parts of the grid, batteries can provide power to homeowners and businesses.

“The grid becomes more stable,” Olinsky-Paul said. “You’re increasing reliability and resiliency.”

However, while the possibilities offered by batteries are exciting interest, these storage systems are generally not as widely subsidized as energy efficiency programs or solar and wind energy, the Clean Energy Group report notes. Changing the standards to include peak demand reduction under the umbrella of energy efficiency allows states to tap existing programs to support batteries.

The potential environmental benefits of promoting storage in this way, however, are not yet fully clear.

Hittinger notes the benefits storage can have by lowering peak demand. However, even if efforts are made to connect batteries to clean generation sources, storage subsidies are unlikely, at least in the short-term, to do anything to reduce emissions in the state, he said.

“Storage is a net consumer of energy,” Hittinger said. “In Massachusetts, most plausible operations scenarios are probably close to breaking even as far as emissions go.”

Champions of including storage in efficiency programs, however, argue the environmental benefits are not to be discounted. Deploying batteries more widely can help get the most out of solar and wind generation, they note. On sunny days or windy nights, when these systems are generating more power than needed, the excess energy can be stored in batteries, then used later. This stored clean energy can then displace higher-cost fossil fuel generation.

“They’re going to amp each other up in a huge way to deliver local clean energy to help us lower cost, improve quality of the grid, and help the planet,” said Audrey Schulman, founder and executive director of the nonprofit Home Energy Efficiency Team. “It’s a sin not to use it.”

And in the long-term, storage has an important role to play in creating an overall cleaner grid, said Mark LeBel, an associate at the Regulatory Assistance Project, a Vermont-based nonprofit that advises policymakers on clean energy issues. If storage can help lower peak demand, the region’s grid infrastructure could evolve in a cleaner direction. The dirtiest power plants — the ones that only stay in business to serve peak needs — might eventually be able to close down, LeBel noted.

Massachusetts’ move, LeBel said, signals an important change in the way people are thinking about energy efficiency, expanding it to include more comprehensive ways of looking at energy management.

“There’s a little bit of a broader philosophical shift going on,” he said. “There’s certainly a lot of room for storage under energy efficiency program once you realize that it’s about more than just kilowatt-hours.”

Sarah Shemkus

Sarah is a longtime journalist who covers business, technology, sustainability, and the places they all meet. She has covered the workings of small-town government in New Hampshire, the doings of alleged swindlers and con men, and the minutiae of local food systems. Her work has appeared in the Guardian, the Boston Globe, TheAtlantic.com, Slate, and other publications. Sarah covers the state of Massachusetts.