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How to Calculate Maximum Available Kilowatts

A set of rules knows as Ohm's Laws covers most basic electrical calculations. Georg Simon Ohm, a Bavarian scientist, identified the relationship between current, voltage, resistance and power, and published his findings in 1827. Since then, electricians have used the Ohm's laws equation, voltage x current = wattage, to calculate wattage whenever the voltage and current in a circuit are known. To determine the maximum available number of kilowatts, you must first determine the maximum voltage and maximum current.

Instructions

- 1
  Determine the available voltage. For example, in the U.S. your domestic voltage is available at two ratings. The lower voltage lies between 110 and 120 volts, and the higher voltage lies between 220 and 240 volts.
- 2
  Determine the maximum current, or amperage, available. For a power supply protected by a fuse or circuit breaker, the maximum current is the amperage at which the fuse or circuit breaker cuts off the electricity supply. If a cut-off device does not protect the power supply, the current rating of the wiring determines the maximum available current.
  
  For example, a circuit protected by a 30-amp circuit breaker has a maximum possible current of 30 amps, and a cord rated at 20 amps limits the safe current supply to that same value.
- 3
  Multiply the maximum current in amps by the available voltage. The result is the maximum available wattage. For example, 30 amps x 240 volts gives a maximum wattage of 7,200 watts.
- 4
  Divide the maximum watts by 1,000 to convert to kilowatts. The result is the maximum kilowatts available from that voltage and current. For example 7,200 watts is equivalent to 7.2 kilowatts because 7,200 over 100 = 7.2.

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