EV Fast-Charger Demand Charge Shield

Tame utility demand charges for DC fast-charging hubs. Enter your measured peak load and tariff rate to size monthly savings, the battery energy needed to shave a percentage of that peak, and the simple payback on the storage investment.

Highest 15-minute (or similar) interval demand on the utility bill.
Utility demand charge applied per kilowatt of peak demand.
Optional. Defaults to trimming peak demand by 20% when blank.
Optional. Defaults to a 15-minute billing interval.
Optional. Defaults to $550 installed cost per usable kWh.

Demand charge structures vary by utility and rider. Validate assumptions with tariff documents and a qualified energy advisor.

Examples

  • 350 kW peak, $18/kW charge, 20% reduction, 15-minute interval, $550/kWh battery ⇒ Monthly demand charge before mitigation: $6,300.00 • Projected savings at target reduction: $1,260.00 • Battery buffer needed: 17.50 kWh (approx. 70.00 kW shaved) • Simple payback: 7.6 months
  • 250 kW peak, $22/kW charge, 30% reduction, 30-minute interval, $400/kWh battery ⇒ Monthly demand charge before mitigation: $5,500.00 • Projected savings at target reduction: $1,650.00 • Battery buffer needed: 37.50 kWh (approx. 75.00 kW shaved) • Simple payback: 9.1 months

FAQ

What if my utility uses a 30- or 60-minute interval?

Adjust the interval field so the battery buffer scales to the duration over which the demand is measured.

Can I model partial battery participation?

Yes. Lower the target reduction percentage to reflect the portion of peak demand the battery will handle while the remainder is metered.

Does the payback include battery degradation?

No. Incorporate cycle life and augmentation costs separately when finalizing project economics.

How do managed charging incentives factor in?

Layer incentive dollars onto the monthly savings figure to shorten the payback or justify a larger battery.

Additional Information

  • Battery buffer sizing assumes the reduction must be sustained for one billing interval equal to the selected minutes.
  • Simple payback divides installed battery cost by monthly demand-charge savings and does not account for incentives or financing.
  • The calculator isolates demand charges; energy (kWh) charges and managed charging incentives should be layered on separately.

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