Keeping refrigerator door closed saves energy

Just about everyone in the U.S. has heard the words: “Close the refrigerator door.” Stereotypically, this is associated with an indecisive teenager.

How important is that closed door, really? Is it still important, given how much fridges have improved?

If you are using a really old fridge as your primary fridge, replacing it will save money in the long run. The easiest way to save money on refrigeration is to replace any fridge built more than 20 years ago with a new EnergyStar-rated refrigerator.

In the 1970s, a refrigerator might have consumed 2,200 kilowatt-hours a year. By the 1990s, improvements in insulation and the heat pumps used in refrigerators had reduced that to about 1,100 kWh/year. Today, a good refrigerator might only use 300 kWh/year. (For reference, an average home in the greater Puget Sound area uses about 900-1,100 kilowatt-hours a month for all electric uses. This does not reflect a home’s entire energy budget if it also uses gas or propane.)

Fridges can last a long time, and new ones are expensive. You may want to keep an older refrigerator for the additional capacity, or for use in a space like a garage.

In places like Florida and Texas, a fridge in a hot garage might have to run constantly. It is not as bad here. In the Puget Sound area, fridges in garages without climate control can even be more efficient than an indoor fridge in the winter months, because they only have to work against outside temperatures that are fairly close to the desired temperature inside the fridge, instead of working against a 68 degree home. However, it only takes a few really hot days to significantly increase the total energy used by a fridge in a hot garage. When possible, keep fridges used outside your kitchen in a climate-controlled location, or in a colder location like a basement, so that they don’t have to work against hot outdoor temperatures in warm months. Never put a refrigerator in direct sunlight.

Go back to the teenager with the open refrigerator door. If the door is open, the air temperature in the refrigerator will go up, and the refrigerator compressor will turn on, because the controller senses that the fridge is too warm. An older fridge might need 800 watts, which is about the same as having thirteen, 60 watt lights turned on at the same time. However, most of the mass in the refrigerator is chilled food, which takes a long time to warm up. Once the door is shut again, the small amount of warm air that was let in while the door was open will cool to the desired temperature very quickly.

Keeping an old fridge’s door open for five minutes would use 67 watt-hours, equivalent to running a 60 watt tungsten filament light bulb for a little over an hour. Keeping a new fridge’s door open for five minutes would only use about 17 watt-hours. That’s the equivalent of running a nine watt LED light bulb equivalent to a 60 watt 1970s tungsten filament light, for a little under two hours.

So, keeping the fridge open today, even though it only uses a quarter of the energy of a 1970s fridge, is even worse than it was then!

Close the refrigerator door!