Virtually All Electricity Eventually Becomes Heat

Nov. 14, 2012

When most people think about reducing the energy they use for air conditioning, they only think about keeping outside heat from getting into the house. This is very important, but only half of the problem. What most people don't consider is minimizing the heat being generated inside their houses.

Virtually all energy used eventually becomes heat. Consequently, minimizing electricity use also minimizes the heat generated, which in turn minimizes the need for air conditioning. This is a strong incentive, especially here in Florida, for using the most efficient items possible and use them only when necessary, keeping them off when not needed.

It is obvious to most that items like stoves, ovens, and hair blow dryers are heating up their houses. Not so obvious are things like light bulbs. For example, compact fluorescent lights (CFLs) and LED lights not only consume a quarter of the electricity of an incandescent bulb with the same light output, they also generate one quarter the heat of an equivalent incandescent bulb. Less heat means less need for air conditioning.

Heat pumps, such as air conditioners and refrigerators, do not generate cold. They just remove heat and put it someplace else. “Cold” is really the absence of “heat,” sort of like an “empty” glass of water is a glass where water is absent (You don't generate empty and put empty someplace else!). Since heat pumps have to be less than 100% efficient, they put more heat into that “someplace else” than they removed. For example, refrigerators put the heat they remove from inside them plus operating losses into your kitchen. Air conditioners put that removed heat plus losses outside, so they are effectively heating the outside of your house. This is part of the “urban heat island” effect.

Fans do NOT cool a room, they heat it up. They consume electricity and virtually all their electricity is converted into heat. Their effect is psychological and physiological. They only appear to cool a room if they are blowing on someone who feels it. If no one is in the room to feel the breeze from the fan, all the fan does is waste electricity and heat up the room a little.

All those things you leave on, such as computers, modems, and cable TV boxes, are heating up the space they are in. So are all those “phantom loads,” things that you think are off but are still drawing electricity when idle, such as microwave ovens and battery chargers.

People give off heat; about 100 W per person at rest, more if active. Dietary calories are really a measure of body heat. That is one reason why it feels hotter at parties and other crowded situations.

Fanning yourself actually makes you hotter since you burn energy to move the fan, increasing your power generated. The best way to keep as cool as possible (all else being equal) is to be as relaxed as possible.

So, when people say that the reason I use so little electricity in my house is because I don't use air conditioning, they are partly right. I do use a lot less air conditioning than most Floridians simply because I don't need to because I have a lot less stuff inside my house heating it up.