MayClaire01
New Member
It's a myth that leaving the AC on while you're away at work uses less energy than turning it on when you get home. Here's why:
Heat goes to where it's not. That's why heat from outside goes into your cooler home. With the AC off, at some point your house will be so hot it can't absorb any more heat. When you come home and turn the AC on, the AC removes all that heat.
But if the AC is on when you're gone, then you've turned your house into a heat magnet. But keeping it artificially cool, there's no limit to the amount of heat it can absorb. It can always absorb more heat. And your AC has to remove that heat constantly. Your AC kicks in and removes some of that heat, then the house is cooler so it sucks in more heat from outside, so your AC kicks in again and removes that heat, and so on.
This means that throughout the day, your house has absorbed way more than one houseful of heat. And your AC had to remove it all. By contrast, with the AC off all day, then it has to remove just one houseful of heat when you come home and turn it on.
Let's say you leave the AC off, and your house absorbs 20k BTU's of heat and then stops, because that's all it can absorb.
Now let's say that you have the AC running instead. The house absorbs 5k BTU's of heat, so the AC kicks in and removes it. Then it absorbs another 5k BTU's, and your AC kicks in and removes that. Repeat that process several times during the day.
The actual numbers will vary, and I haven't tested this to see exactly how much the penalty for leaving the AC on during the day is, but there is zero question that running the AC all the time uses more energy than turning it on when you get home. This is not a gray area, it's simple physics, and no person with any knowledge of this subject disputes it. Running the AC when you're not home wastes energy, period.
Heat goes to where it's not. That's why heat from outside goes into your cooler home. With the AC off, at some point your house will be so hot it can't absorb any more heat. When you come home and turn the AC on, the AC removes all that heat.
But if the AC is on when you're gone, then you've turned your house into a heat magnet. But keeping it artificially cool, there's no limit to the amount of heat it can absorb. It can always absorb more heat. And your AC has to remove that heat constantly. Your AC kicks in and removes some of that heat, then the house is cooler so it sucks in more heat from outside, so your AC kicks in again and removes that heat, and so on.
This means that throughout the day, your house has absorbed way more than one houseful of heat. And your AC had to remove it all. By contrast, with the AC off all day, then it has to remove just one houseful of heat when you come home and turn it on.
Let's say you leave the AC off, and your house absorbs 20k BTU's of heat and then stops, because that's all it can absorb.
Now let's say that you have the AC running instead. The house absorbs 5k BTU's of heat, so the AC kicks in and removes it. Then it absorbs another 5k BTU's, and your AC kicks in and removes that. Repeat that process several times during the day.
The actual numbers will vary, and I haven't tested this to see exactly how much the penalty for leaving the AC on during the day is, but there is zero question that running the AC all the time uses more energy than turning it on when you get home. This is not a gray area, it's simple physics, and no person with any knowledge of this subject disputes it. Running the AC when you're not home wastes energy, period.