First, per the "Howstuffworks" website
The thermal energy content of coal is 6,150 kWh/ton. Although coal fired power generators are very efficient, they are still limited by the laws of thermodynamics. 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.
That made me look at my utility bill. On average, my family uses about 800 kWh a month.
800 kWh X 12 months = 9,600 kWh per year / 2,460 kWh = 3.90 tons X 2,000 lbs in one ton = 7804 pounds of coal to run my house per year.
That's alot of coal.
As far as the price of coal. It appears that for the Uinta Basin, the going price is about $73.00 a ton.