Having done as... careful a Googling as I could, I've got some vague numbers.
A ton of coal will generate about 2500kWh. A coal plant will burn 1.4 million tons a year.
A single human will generate 100-150kWh. Average human weight worldwide is 62kg, so you get 16 humans to the ton, and 1600-2400kWh per ton of human. You'd need to burn somewhere on the order of 25 million humans per plant per year to keep up.
I'm not going to work the numbers any further than that, but I'm sure you can all extrapolate.