Summary:
- Net energy is the amount of useable energy available from a resource after subtracting the energy needed to make the energy from that resource available.
- The energy cost of an energy resource increases when the easy deposits of that resource have already been consumed.
- Solar energy yields much more net energy than other sources because it takes very little energy to get usable solar energy.
- The efficiency of coal-fired electricity is greater in areas where the coal is locally mined and does not have to be transported great distances.
- Energy efficiency describes how much useful work is extracted from one unit of energy.