Hospitals are energy hogs.

With their 24/7 lighting, heating and water needs, they use up to five times more energy than a fancy hotel.

Executives at some systems view their facilities like hotel managers, adding amenities, upscale new lobbies and larger parking garages in an effort to attract patients and increase revenue. But some hospitals are revamping with a different goal in mind: becoming more energy-efficient, which can also boost the bottom line.

“We’re saving $1 [million] to $3 million a year in hard cash,” said Jeff Thompson, the former CEO of Gundersen Health System in La Crosse, Wis., the first U.S. hospital system to produce more energy than it consumed in 2014. And, he said, “we’re polluting a lot less.”

The health care sector — one of the nation’s largest industries — is responsible for nearly 10 percent of all greenhouse gas emissions, hundreds of millions of tons worth of carbon each year. Hospitals make up more than one-third of those emissions, said researchers at Northeastern University and Yale.

Increasingly, though, health systems are paying attention:

• Gundersen Health System in Wisconsin employs wind, wood chips, landfill-produced methane gas and even cow manure to generate power, reporting more than a 95 percent drop in its emissions of carbon monoxide, particulate matter and mercury from 2008 to 2016.

• Boston Medical Center analyzed its hospital for duplicative and underused space, then downsized while increasing patient capacity. It now has a gas-fired 2-megawatt cogeneration plant that traps and reuses heat, saving money and emissions, while supplying 41 percent of the hospital’s needs and acting as a backup for essential services.

• Theda Clark Medical Center in Wisconsin is saving nearly $800,000 a year — 30 percent of its energy costs — after making changes that included retrofitting lights, insulating pipes, taking the lights out of vending machines and turning off air exchangers in parts of its building after hours.

• Kaiser Permanente aims to be “carbon-neutral” by 2020, mainly by incorporating solar energy at up to 100 of its hospitals and other facilities.

While the environmental benefits are important, “what I’ve seen over the years is cost reductions are the prime motivator,” said Patrick Kallerman, research manager at the Bay Area Council Economic Institute, which released a report on ways the hospital industry can help states reach environmental goals. Some of its recommendations are simple: replacing old lighting and windows. Others are more complex: powering down heating and cooling in areas not being used and updating ventilation standards first set back in Florence Nightingale’s day.

When Bob Biggio was hired in 2011 to oversee Boston Medical Center’s facilities, hospital leaders were about to launch a redesign. Yet the hospital was also facing financial struggles. He put the move on hold while analyzing how the hospital was using its space.

“My first impression with data I had gathered was our campus was about 400,000 square feet bigger than it needed to be, Biggio said. “A square foot you never have to build is most efficient of all.”

The new design is smaller but more efficient, handling 20 percent higher patient volume. It also cut power consumption by 42 percent from a 2011 baseline.

But how to sell that in the C-suite? “At no point did I mention climate change or polar bears,” Thompson said.

Instead, he focused on the organization’s mission to improve health — and the potential cost savings. “There are multiple examples … where, if we’re thoughtful, we can improve the local economy, lower the cost of health care and decrease the pollution that is making people sick,” he said.