... Matter is able to exist forever until it gets changed into energy at the rate of e=mc2. But in current practice, we are unable to even come close to this rate.

Currently, the efficiency of matter to energy conversion of todays fuels are beyond pitiful. According to coaleducation.org it takes 2205 lbs of coal to make 2500 kwh’s of electricity. And is from this source that I base my efficiencies. Now if we do a little math we come up with a few numbers,

-2,500 kwh the amount of electrical power gained from one tonne of coal today

- 2,500 Gwh the maximum amount of electrical power possible to derive from one tonne of coal.