MIL-HDBK-1003/7
Utility Power Rates. Utility power rates are based on the utility's costs to
21.5.4
provide both electrical capacity and energy. This is reflected in the billing as
charges for electrical demand and energy.
21.5.4.1 Demand Charge. The electrical demand for billing purposes is usually
determined from demand instruments located at the customer facility such as a kW meter
and associated printing recorder which periodically records the kW load or demand. In
some cases, the demand may be determined by tests made by the utility. Billing demand
is usually established on a monthly basis and is taken as the highest demand recorded,
usually in any 30-minute interval. Many utilities' rate schedules also contain a
ratcheted demand clause which establishes a minimum billing demand based on the highest,
or some percentage of the highest, demand occurring in the previous 12 months, or some
other chosen period. The effect of the ratchet may result in a billing demand for a
month of low demand, for instance a winter month, that is based on a high demand in a
previous summer month. Rate schedules take various forms, depending on the utility and
state public utility commission practices. Rate schedules for demand will vary
according to geographic area and usage.
21.5.4.2 Energy Charge. The energy usage for billing purposes is determined from kWh
meters located at the customer's facility. Energy charges are usually tied to billing
demand in such a manner that low energy use at a high demand is charged at a high rate
whereas a large energy use at a low demand is charged at a lower rate. Therefore any
peak shaving scheme which can be used to reduce demand can result in savings which may
economically justify the investment costs for peak shaving equipment and its fuel usage,
operation, and maintenance. Rate schedules for energy will vary according to geographic
area and usage.
21.5.4.3 Total Electric Billing. The electric billing by the electric utility is
usually computed and issued on a monthly basis. The total electric bill will usually be
the sum of the demand and energy charges plus adjustment for such items as fuel cost,
research and development surcharge, and taxes.
21.5.4.4 Other Factors for Sale of Electricity. The rates charged for electrical
demand and energy depend on other factors or the type of service. These are typically
as follows:
a)
Service at secondary voltage.
b)
Service at primary voltage (12,000 to 69,000 volts).
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