What is COP and why is it not the same as efficiency?

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Multiple Choice

What is COP and why is it not the same as efficiency?

COP shows how much heat is moved per unit of electrical energy you put in. For a refrigerator, it’s the amount of heat removed from the inside divided by the electrical energy the device uses. Because you’re transferring heat rather than producing it, a small amount of input energy can move a lot of heat, so COP can be greater than 1. This is why COP isn’t the same as efficiency—efficiency usually compares useful energy output to energy input, but in a fridge the “useful effect” is removing heat, not creating heat, so you can’t directly equate COP with a typical efficiency measure. For example, you could move 100 units of heat out while using only 20 units of energy, giving a COP of 5. The other statements mix up what COP measures (it’s not the ratio of input to output, it isn’t restricted to less than 1, and it isn’t about heat produced).

COP shows how much heat is moved per unit of electrical energy you put in. For a refrigerator, it’s the amount of heat removed from the inside divided by the electrical energy the device uses. Because you’re transferring heat rather than producing it, a small amount of input energy can move a lot of heat, so COP can be greater than 1. This is why COP isn’t the same as efficiency—efficiency usually compares useful energy output to energy input, but in a fridge the “useful effect” is removing heat, not creating heat, so you can’t directly equate COP with a typical efficiency measure. For example, you could move 100 units of heat out while using only 20 units of energy, giving a COP of 5. The other statements mix up what COP measures (it’s not the ratio of input to output, it isn’t restricted to less than 1, and it isn’t about heat produced).

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