There are two generator power markets – standby (emergency) power and prime power.  Prime power means that the generator is the sole source of electrical power and runs whenever power is needed.  For example, at a coal mine, this might be 8 hours a day. Meanwhile, standby power is used only during emergency situations. Many would argue that because this a generator that is rarely used, it doesn’t justify the investment.  The savings equate to kW-hr savings.