How effecient is the human body?

Question

how much energy does the human body use during an average days work? how does it compare with the energy contained in a gallon of gasoline?

Answer 1

well, you can't really compare these two since one uses energy while the other is a source for it.

in general, bodies use ~8000000 joules a day whereas a gal of gas can give off 1300000000 joules

Answer 2

depends on type of activity, for example 1/2 hr  slow walking is equal to about 120 calories.