Calculate the operating cost per hour of a motor that has a power factor of 85% and consumes 15 kW per hour (active power as measured by a wattmeter) if the power rate is $0.105/kWh. A. First, calculate the apparent power. This is the actual amount of power that the power company must supply to the motor. This is found as follows: PA = (VA) PF = 0.85= P P 15,000 0.85 15,000 P A where == 0.000057 = 1 P= 17,647 VA or 17.647 kVA Now the cost can be calculated. B. Calculate the cost using the Power Cost formula. The cost of electrical power is based on the number of kilowatts consumed per hour, or kilowatt hours (kWh). You can determine the cost per hour of the power consumed using the following Power Cost formula: P hr 1 Ch = hr C P kWh POWER COST FORMULA Cr=Px C hr hr kWh Operating cost per hour ($/hr) = Power consumed per hour (kWh) = Cost per kilowatt hour ($)