Generally speaking, the amount due on the bill is sub-divided as follows:
- fixed quote cost related to the available power (kW)
- consumed energy quote cost related to the active power consumed (kWh)
- reactive energy quote cost related to the reactive power consumed (kWarh)
The electricity supply utility provides the maximum power capacity to be used over an average of 15 minutes; in practice, a certain amount of power is made available (kWh) for use every 15 minutes (contractual power: 4 = power to be used in 15 minutes) and any excess value results in an automatic recalculation of the bill for the entire month or sometimes even the entire year.
Thus it can be seen that a slightly increased power consumption over just one quarter of an hour period throughout the entire year can determine the maximum power consumed over that year, and that it is the amount of time the equipment is operating simultaneously, rather than the total rating of the equipment in kW, that is important