Private in-browser planning
Peak Demand Charge Estimator
Starting values are hypothetical. Replace them with your own figures. Inputs stay in this browser and are not included in the energy inquiry.
- Use only when the tariff bills the maximum of the stated three quantities.
- No tariff rule, ratchet lookback or seasonal interpretation is inferred.
Measured demand may differ from billed demand
Measured demand records the account’s highest applicable interval load. Billed demand is the quantity the tariff uses for a particular charge, which may include a minimum or a historical reference. Reducing the current measured peak may leave billed demand unchanged while a larger floor remains in effect. This distinction can materially change a demand-management case.
Locate the precise rate schedule and component on the current bill. Confirm whether the quantity is kW or kVA, the measurement window, season, rounding method and any adjustments. A bill with several demand components may require separate calculations. This tool assumes one dollars-per-kW charge with the stated simple maximum-of-three rule.
How the modeled billing quantity is selected
First multiply the historical peak by the entered ratchet percentage. Then compare that result with the current measured kW and the minimum kW. The largest value becomes modeled billed demand. Multiply it by the demand rate to obtain the modeled charge for one billing period. Setting the historical peak and minimum to zero removes those floors from the scenario.
For illustration, measured demand of 150 kW, a 100 kW minimum and an eighty-percent ratchet on a 200 kW historical peak produce a 160 kW floor. Modeled billed demand is therefore 160 kW. At an invented $15 per kW rate, the component costs $2,400 even though the current measured maximum was only 150 kW.
Check the ratchet reference and lookback
A historical peak is not an arbitrary largest value from an old bill. The actual tariff defines which months, seasons, measurement windows and lookback period apply. Enter the reference it specifies. If a historical peak rolls out of the lookback or a new high peak is established, future billing floors may change. This static estimator does not advance that history month by month.
Do not use the percentage field to approximate an unexplained bill difference. Ask the utility to identify the billing determinants when measured and billed figures disagree. Some structures use contract demand, transformer capacity, kVA or power-factor adjustments that are outside this model and cannot be accurately reproduced with an invented ratchet percentage.
Use the result in a realistic demand scenario
When exploring load controls, calculate the original billed demand and the proposed billed demand under the same tariff logic. A physical reduction only creates savings in this component if the resulting billed quantity decreases. Carry those two billed amounts to the demand-charge savings tool and count only periods in which the change actually applies.
Review the rest of the bill before concluding that a component difference equals total bill savings. Energy use, time-of-use charges, multiple peaks and operational constraints can also change. Keep tariff excerpts, relevant peak history and interval evidence with the calculation. This estimator provides arithmetic for an explicitly chosen rule; it does not validate that rule, forecast future peaks or guarantee a utility adjustment.
Sources & scope
Primary references reviewed October 15, 2026. These sources support the stated concepts; actual tariffs, program rules and signed agreements govern the account. Decision examples and operational worksheets are original educational analysis.
- DOE FEMP: Evaluating Your Utility Rate Options
Energy charges, demand charges, fixed charges and tariff structures; practical limits of simplified rate calculations.