185 Calculation Of A Monthly Bill

Following is the basic formula used for calculating the monthly bill under a utility rate. The sum of these components will result in the monthly bill.

1) Customer Charge

• Customer charge = fixed monthly charge

2) Energy Charge

• Energy charge = dollars x energy use

• Energy/Fuel Cost Adjustment = dollars x energy use

3) Demand Charge

• Demand charge = dollars x demand

• Reactive Demand Charges (electric only) = dollars x measured kilovolt-ampere reactive demand

4) Tax/Surcharge

• Tax/surcharge = either sum of one or more of items 1-3 above multiplied by tax percentage, dollars x energy use, or dollars x demand

Some examples illustrating the calculation of a monthly bill follow. These examples are actual rate schedules used by the utilities shown. The information regarding the consumption of electricity used in the sample calculations are based on the typical figures shown in Table 18.1.

18.5.1 Commercial General Service with Demand Component

The commercial general service rate often involves the use of demand charges. Table 18.2 provides rate data from Public Service Electric & Gas Company. A sample bill is calculated using the data from Table 18.1 for a convenience store.

Energy Usage - 17,588 kWh; Billing Demand - 30 kW; Season - Summer (June)

Customer Charge: $3.74

Energy Charge: $1,661.01

17,588 kWh x.09444 Energy Cost Adjustment: -$302.37

17,588 kWh x <.017192> Demand Charge: $262.34

Total Monthly Charge: $1,624.72

Energy Usage Measured in kWh per kW Demand

The standard measure of electric energy blocks is in kilowatt hours. An alternative measure used by electric utilities for commercial and industrial rates is energy per unit of demand (e.g., kWh per kW). This block measurement is illustrated by Virginia Power's Schedule GS-2 Intermediate rate in Table 18.3. We are calculating the bill for October use. According to Table 18.1, the convenience store used 16,003 kWh in October and had a billing demand of 32 kW. The bill for this use is as follows.

Customer Charge: $21.17

Energy Charge:

Block 1 - (150 kWh x 32 kW), or 4,800 kWh @ $0.04840 = $232.32

Table 18.1 Typical usage patterns.
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