Calculation sequence
Step-by-step method
- Multiply user-entered billing demand by the demand rate.
- Multiply by the whole number of billing periods.
- Review the serving tariff before use.
ElectricalBeginnerEnergy and Demand
Demand-Charge Estimation Calculator
Estimate simple demand charges from a user-entered billing demand, rate, and number of periods.
Why it matters: Demand charges can be material, but the serving tariff—not a generic formula—defines the bill.
Calculated result
Engineering evaluation
Estimated total demand charge (Cᵀ)90,000 currency
- Demand charge per period (Cᵖ)
- 7,500 currency/period
Engineering interpretation
The simple demand-only screen is 7500 currency units per period and 90000 for 12 periods.
Important limitations
- The serving tariff controls. Ratchets, TOU windows, seasons, coincident peaks, minimum bills, taxes, and PF adjustments are omitted unless represented in the entered values.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
Cᵖ = Pᵇ·Rᵈ
Cᵀ = n·Pᵇ·Rᵈ
Current substitution
Cᵖ = 500×15 = 7500; Cᵀ = 12×7500 = 90000.
Equation legend
Inputs and calculated quantities
- Pᵇ
- Billing demand — kW
- Rᵈ
- Demand rate — currency/kW-period
- n
- Number of billing periods — count
- Cᵀ
- Estimated total demand charge — currency
- Cᵖ
- Demand charge per period — currency/period
Applications
How this calculation is used
Building design
Screen a simple demand-cost relationship.
Construction
Check meter and tariff assumptions.
Commissioning
Estimate demand-only cost using visible user-entered values.
Quality controls
Assumptions and limitations
Assumptions
- Entered values describe one stable operating condition and use a consistent electrical or metering boundary.
- Measured quantities are simultaneous, representative, and obtained with appropriately rated instruments.
Limitations
- Serving utility tariff and bill definitions control.
- Ratchets, time-of-use windows, seasonal rates, coincident peaks, minimum bills, taxes, and PF adjustments are omitted unless represented in the entered values.
Field use
Verification procedure
- Follow the approved electrical-safety program and use correctly rated instruments.
- Confirm wiring, ratios, units, operating mode, and measurement boundaries.
- Document simultaneous readings and compare with approved project and manufacturer data.
Common engineering mistakes
- Combining values from different time intervals, phases, or measurement boundaries.
- Treating a screening result as equipment selection, protective-device coordination, or code compliance.
Technical basis
References and source standards
- U.S. Department of Energy—Energy Saver and Better BuildingsFederal energy-management, lighting, motor, and building-energy guidance.
- NIST Guide for the Use of the International System of UnitsElectrical quantity, unit, symbol, and conversion context.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement