When you’re standing in the grocery store, staring through a cooler door, trying to decide whether to buy oat, soy, almond or coconut milk, there’s one thing that’s probably not on your mind: The enormous carbon footprint of commercial refrigeration.

"Refrigeration is energy intensive because it takes a lot of energy to remove heat. And we don't think about it when we’re shopping at a grocery store," said Danielle Wright, executive director of the North American Sustainable Refrigeration Council. "Those systems have to be running 24/7. The food supply chain in general is so energy intensive, and it’s so hidden from public view."

Indeed, the United Nations estimates that the refrigeration sector accounts for 17 percent of global energy consumption. In the U.S., the average commercial refrigerator gobbles up 17,000 kilowatt-hours of electricity per year — almost double that of an average American home, according to one estimate. Commercial freezers, meanwhile, can draw down 38,000 kilowatt-hours annually — or about quadruple the average American home.

Multiply that by many, many refrigerators per grocery store, across 40,000 grocery stores in the U.S., and commercial refrigeration becomes a huge burden on the electrical grid. That’s why there’s a growing movement, led by organizations such as the NASRC, to make those big fridges and freezers more efficient and ultimately more sustainable.

"It started out with simple things," Wright said. Grocers started adding plastic curtains overtop open fruit and vegetable cases to reduce temperature loss overnight. They’ve also more broadly adopted doors for standing fridge cases, overcoming an initial hesitation that they would reduce sales (the opposite happened, according to Wright). "That’s a huge energy saver that's kind of obvious," she said.

But a lot of the efficiency gains happened behind the scenes, in the part of fridges that shoppers never see: the mechanical components. Everything from compressors to condensers and motors have become more efficient in recent years, while the control systems have become more sophisticated, allowing the units to stay cool with less strain on the system.

There’s just one problem. Unlike a fridge in your house, where you can swap in a new, Energy Star model in one fell swoop, commercial fridges are huge, custom-built behemoths that are not easily replaced.

"The system is only as good as the sum of its parts, and no two systems are going to be identical," Wright said. And it’s rare that a whole system would go down at the same time. It’s more common that parts will be upgraded and replaced as needed; a new compressor one year, a new condenser a couple of years later.

"It’s never like, the whole system gets an upgrade. You kind of have this Frankenstein effect, where the different components are different ages," Wright said.

Financial incentives from local utilities can push grocers toward adopting more efficient parts when the opportunities do arise. Wright said upgrades that often star