If you’re a hawk about refrigerator energy efficiency, you probably already do things like keep your fridge and freezer mostly full, clean the coils regularly and avoid browsing for snacks with the door open. But one tactic can be a bit of a tightrope walk: how long should you wait before putting hot leftovers into the fridge?

Heat Wave

If it wasn’t for energy efficiency concerns, there would really be nothing wrong with putting hot foods directly into most modern refrigerators. Doing so won’t damage the appliance in any way, and it won’t cause the other food inside to spoil.

But it will cause a significant spike in the temperature inside the fridge, placing a large burden on your refrigerator’s compressor as it works to bring the temperature back down. To do this every once in a while won’t be a major drag on your household energy efficiency, but if you regularly store freshly cooked leftovers, it’s important to have a plan for minimizing this waste.

Food Safety First

Protecting your refrigerator’s energy efficiency is a simple matter of making sure leftovers are mostly cool before putting them inside. But it’s critically important to not leave food sitting out for too long, or bacteria can develop and lead to foodborne illnesses like salmonella or E. coli. The FDA recommends that cooked foods remain unrefrigerated for no longer than two hours, or one hour if the room temperature is 90 degrees Fahrenheit or higher.

If you have to choose between putting still-warm foods in the refrigerator or letting them cool on the counter a little longer, go the food safety route. Two hours is usually plenty of time to allow foods to cool, but there are a couple of tricks that can help foods cool faster.

First, you can put the hot leftovers in a covered dish and set it in a shallow bath of ice water in your sink -- just be sure the water doesn’t get into the dish. A few minutes of this will rapidly cool down even piping-hot foods.

Second, if your leftovers are mostly liquid like soups or stews, split them up into multiple shallow containers. Make sure the food is less than two inches deep. This will speed cooling on the counter, and it will help the leftovers cool more rapidly and evenly in the fridge.

The Olden Days

If you’ve been given time-tested advice against putting warm leftovers in the refrigerator, there may be a reason for that: older refrigerators are less powerful, and the heat from warm food used to be hot enough that it could raise the temperature to an unsafe level. So if your grandmother remembers this practice, that doesn’t mean you need to follow the same rules with your modern fridge.

Looking for more ways to save energy? Consider calling your local electricians to schedule an energy audit of your home.