Question: how much energy is in coal?
Answer: Only about 40 percent of the thermal energy in coal is converted to electricity. So the electricity generated per ton of coal is 0.4 x 6,150 kWh or 2,460 kWh/ton. To find out how many tons of coal were burned for our light bulb we divide 876 kWh by 2,460 kWh/ton. That equals 0.357 tons.