The cost of electrical energy is a function of the amount of energy consumed and the size of the peak demand. The unit of electrical consumption is the kilowatt-hour, which is measured by a watt-hour meter. To calculate the monthly electric bill, the utility company reads the electric meter and determines the number of kilowatt-hours of electricity consumed since the last reading. This amount is multiplied by the appropriate scheduled rate to determine the usage charge. The demand charge reflects the peak number of kilowatts required by the property during a specific, short-term time period. The demand is also read monthly from the utility meter, with the additional charge added to the electric bill on the basis of a demand rate schedule.