Monthly Electricity Bill Calculator

A monthly electricity bill calculator estimates the total amount billed for electric service by separating energy consumption, demand billing, fixed utility charges, and taxes or fees. The primary output is the Estimated bill, along with the Effective rate in dollars per kWh.

For electrical contractors, facility personnel, and load-planning teams, the estimated bill supports operating-cost review for a service, feeder, motor load, HVAC equipment change, or process addition. It does not determine conductor ampacity, AWG or kcmil selection, raceway fill, overcurrent protection, voltage drop, or code compliance. Those electrical design decisions require separate load calculations, equipment data, conductor temperature ratings, installation conditions, and AHJ requirements.

The calculator keeps each billing component visible rather than treating the utility bill as one blended rate.

Billing Inputs

Enter the billing information using the same units shown on the utility tariff or statement.

Input	Unit	Electrical billing purpose
Monthly energy	kWh	Total energy consumed during the billing period
Energy rate	$/kWh	Unit price charged for energy consumption
Fixed monthly charge	$	Monthly customer, service, meter, or account charge included as a fixed dollar amount
Billing demand	kW	Billed peak demand when the applicable tariff includes a demand charge
Demand charge	$/kW	Price charged per billed kW of demand
Tax and fee percent	%	Combined percentage applied to the calculator subtotal

Monthly energy is measured in kilowatt-hours, not kilowatts. A 20 kW load operating for 50 hours consumes 1,000 kWh, while its billing demand may be based on a separate utility demand interval and tariff method.

Billing demand is a power quantity in kW. It commonly reflects the highest metered demand during a billing interval, but the exact interval, ratchet provisions, power-factor treatment, seasonal pricing, and demand definition must be taken from the applicable utility tariff. The calculator applies the entered value directly; it does not derive demand from monthly kWh.

Bill Formula

The calculation uses the entered rates and charges as follows:

\(\displaystyle \text{Energy charge} = \text{Monthly energy} \times \text{Energy rate}\)

\(\displaystyle \text{Demand charge} = \text{Billing demand} \times \text{Demand charge}\)

\(\displaystyle \text{Subtotal before tax} = \text{Energy charge} + \text{Demand charge} + \text{Fixed monthly charge}\)

\(\displaystyle \text{Taxes and fees} = \text{Subtotal before tax} \times \frac{\text{Tax and fee percent}}{100}\)

\(\displaystyle \text{Estimated bill} = \text{Subtotal before tax} + \text{Taxes and fees}\)

\(\displaystyle \text{Effective rate} = \frac{\text{Estimated bill}}{\text{Monthly energy}}\)

The Effective rate includes fixed charges, demand charges, and the entered tax-and-fee percentage. It will therefore differ from the entered Energy rate, sometimes substantially. It is a useful blended operating-cost figure for comparing months, evaluating equipment energy use, or screening the economic effect of load reductions.

Calculation Example

Using the entered values:

Input	Value
Monthly energy	1,000 kWh
Energy rate	$0.16/kWh
Fixed monthly charge	$20
Billing demand	25 kW
Demand charge	$12/kW
Tax and fee percent	8%

The calculated billing components are:

\(\displaystyle \text{Energy charge} = 1{,}000 \text{ kWh} \times $0.16/\text{kWh} = $160\)

\(\displaystyle \text{Demand charge} = 25 \text{ kW} \times $12/\text{kW} = $300\)

\(\displaystyle \text{Subtotal before tax} = $160 + $300 + $20 = $480\)

\(\displaystyle \text{Taxes and fees} = $480 \times 0.08 = $38.40\)

\(\displaystyle \text{Estimated bill} = $480 + $38.40 = \text{$518.40}\)

\(\text{Effective rate} = \frac{$518.40}{1{,}000\text{ kWh}} = $0.5184/kWh\)

Although the entered energy rate is $0.16/kWh, the effective rate is $0.5184/kWh because the 25 kW demand charge, fixed monthly charge, and taxes are distributed across the 1,000 kWh monthly energy total.

Electrical Cost Review

The calculator is useful when reviewing electrical changes that affect energy use or peak demand.

A lighting retrofit, motor replacement, HVAC change, VFD application, or operating-schedule adjustment can reduce kWh, kW demand, or both. Reducing kWh lowers the Energy charge at the entered energy rate. Reducing peak demand lowers the Demand charge only when the billing demand is actually reduced under the utility’s tariff and metering rules.

For example, reducing a continuous process load may lower monthly kWh without changing the facility’s peak billing demand. In that condition, the energy charge may fall while the demand charge remains unchanged. Conversely, shifting simultaneous large loads can reduce peak kW demand even when monthly kWh changes very little.

The result can also support preliminary life-cycle cost comparisons for electrical equipment. It should be paired with the equipment’s actual load profile, duty cycle, measured demand, power factor where applicable, utility rate schedule, and expected operating hours.

Utility Statement Verification

The calculator applies a straightforward monthly arithmetic model. Verify the actual utility statement and tariff when the account includes any condition not represented by the listed inputs, including:

• Time-of-use or seasonal energy rates
• Multiple demand periods or demand rate tiers
• Demand ratchets or contract-demand provisions
• Power-factor penalties or reactive-power billing
• Fuel, transmission, delivery, rider, or regulatory charges calculated separately
• Credits, minimum bills, net metering, or demand-response adjustments
• Tax treatment that differs among individual bill line items

Use the utility’s billed kWh, billed kW, and applicable charges for the closest estimate. The result is an estimated monthly electric bill and does not replace the utility statement.