By: Brian Schutt
Since the invention of air conditioning, this question’s been around. What will save me more, to leave my air conditioning on when I’m away, turn up the thermostat, or turn off the air conditioner completely?
A conundrum indeed. And once you’ve likely heard different people give different answers. Here are some of the variables and factors that make this not a black and white issue, but rather a custom answer for your home.
One is the size of your home. Smaller homes will draw less energy and take less time to cool down.
Another factor is the size, efficiency, and insulation of your system and home. This was likely determined by whoever built your home and installed your system. In the linked article, Bob Vila gives a thorough analysis of the impact HVAC system size and proper insulation can have on your home’s energy costs.
Another, and probably the most important variable, is the outside temperature. This is pretty basic, but if the weatherman tells you it’s going to be a high of 75 vs. a high of 85, your decision becomes easier. If it’s 75 outside, it’s not going to get hotter inside, and thus cooling your place when you get home will not take as much time and not take as much energy.
However, on those muggy 85-degree days that we face in Central Indiana, the choice may not be clear. So, we suggest doing a little experiment. Requirements: pen, paper, ability to read the electric meter. On two-three like days do the following:
- Note the reading on your meter before leaving work
- Day 1: leave A/C at your preferred temperature (for my wife and I it’s 72 degrees) Day 2: Turn your A/C up to a higher temperature like 80 degrees Day 3: Turn off A/C completely.
- For days 2 and 3, return your thermostat to a comfortable temperature on your return home.
- After the thermostat returns to your desired temperature or a few hours after your return home, go back to the meter and note its reading.
At this point, just do the addition to see how much electricity you’ve used to get back to comfortable. Whichever uses less energy, saves you the most money, and is the customized answer to the age-old question.
* A side note and helpful hint are that for every degree above 80, you save roughly 3% on energy. Ergo, and moving from 80 to 85, should save roughly 15%.
And now you know the answer to the question: Should I turn off the air conditioner when not home?