Human wattage

A typical person consumes 2000 kcal of food in a day, and converts nearly all of that directly to heat. Compare the person's heat output to the rate of energy consumption of a 100-watt lightbulb.

Looking up the conversion factor from calories to joules, we find

for our daily energy consumption. Converting the time interval likewise into mks,

Dividing, we find that our power dissipated as heat is 90 J/s = 90 W, about the same as a lightbulb.