Walgreens has a net-zero-energy drug store, and now McDonald’s Corp. is wondering whether it, too, might reap the energy and PR rewards of a similar effort.

The world’s largest restaurant chain brought in the Rocky Mountain Institute (RMI) to help it study the possibility of net-zero outlets in three U.S. cities. Although the company isn’t promising anything immediate, an announcement prepared by the RMI quoted McDonald’s as saying that net-zero operation was feasible even without changes to the chain’s menu or service.

Although the study is intended to help restaurants globally, researchers studied three specific cities–Chicago, Washington, D.C, and Orlando, Fla.–specifically to see how net-zero performance could be coaxed out of restaurants with big, busy kitchens and serious HVAC systems.

“The study demonstrates that for high energy intensity building types, such as restaurants, every single piece of energy-using equipment must be examined as part of the system,” said RMI’s Stephen Doig. “There’s plentiful opportunity to optimize and reduce energy use without compromising the consistency and quality of the end products.”

Big improvements in efficiency would be required

Most of the focus of the report covers improved efficiencies for two of the biggest energy users in a typical McDonald’s restaurant: the kitchen and HVAC equipment. For starters, hitting net-zero performance would require a 60% improvement in energy efficiency compared to an “already efficient” U.S. prototype restaurant design from 2013.

Other conclusions:

• After efficiency upgrades, the restaurants would be able to provide all of their power on-site with a 300kw photovoltaic (PV) system over the building and the parking area.
• A combination of more efficient equipment and PV would reduce energy costs to between 5% and 15% of current average use.
• Most of the capital costs needed for the switch would go to PV.

One of the biggest challenges would be reducing or eliminating standby energy use–that is, the energy used by appliances when they are not actually cooking anything–according to Don Fisher of Fisher Nickel, a technology research company in the commercial food-service industry.

McDonald’s says there are a number of steps ahead, including more study and the possibility of designing and building a pilot net-zero restaurant to test new technologies.

The company didn’t announce any particular timetable.