Between fans, portable air conditioners and cooling units running all day through these weeks of intense summer heat, the next electricity bills are set to go through the roof. Look closely at your consumption, though, and you may spot unusual figures you can’t explain even with a home cooling system running non-stop.

The truth is that plenty of other factors quietly push up the final amount. Think of devices left on standby, or appliances with a poor energy rating that draw far more power than today’s top-tier models. But there is one unsuspected habit in particular, one we all repeat every single day, that ranks among the main culprits behind expensive bills.

Why you shouldn’t leave the fridge door open

Few people stop to think about it, but the refrigerator is one of the appliances that consumes the most electricity over the course of a year, because it runs non-stop, 24 hours a day. Opening the door even for a few seconds changes its energy consumption. The reason? With the door open, the cold air stored inside escapes and is replaced by warmer air coming from the kitchen.

The cooling system then detects this temperature swing and fires up the compressor to bring the interior back down. That process requires more energy, and if it happens frequently, the motor has to work harder accordingly.

In the hottest months the effect intensifies further. If the kitchen sits at, say, 28 to 30 °C (roughly 82 to 86 °F), the gap with the inside of the refrigerator is wider than it is in winter. That is why leaving the door open lets in far more warm air, increasing the strain on the compressor and therefore your consumption.

What this habit really costs you

Opening the fridge repeatedly and leaving the door open for long stretches translates into a meaningful increase in monthly electricity costs, on top of accelerating wear on the motor. According to figures compiled by the Institute for Energy Diversification and Saving (IDAE, the Spanish government agency for energy efficiency), prolonged openings can waste up to 7% of total energy consumed.

This single appliance can account for an average of 18% of a household’s annual consumption — a share that rises significantly during the warmer months. The real cost may look small at a glance, but in practice it contributes, and not marginally, to the amount you end up paying.

To minimize the impact, start by planning what you need before you open the refrigerator, so you cut down the time food is exposed to warm air. Another solid tip is to gather everything you intend to eat or drink in a single trip. Finally, organize your food so that it stays visible and easy to find, sparing you a long search with the door hanging open.

Editor’s note

This article was originally published in Italian on money.it by Pasquale Conte on August 15, 2026 as «Bollette alle stelle? Il colpevole potrebbe essere questo gesto insospettabile». It has been translated and adapted for an international audience by the Money.it International desk.