Calculator Inputs
Use the responsive form grid below. Large screens show three columns, smaller screens show two, and phones show one.
Example Data Table
This sample shows a simple 15-minute demand profile and how the highest interval becomes the measured peak used in billing logic.
| Interval | Demand (kW) | Tariff Window | Notes |
|---|---|---|---|
| 08:00 | 540 | Mid-Peak | Warm-up load begins |
| 08:15 | 565 | Mid-Peak | Conveyors and compressors stabilize |
| 08:30 | 590 | Mid-Peak | Packaging area reaches normal load |
| 08:45 | 610 | Mid-Peak | Additional process line starts |
| 09:00 | 645 | On-Peak | Ovens and HVAC overlap |
| 09:15 | 680 | On-Peak | On-peak maximum for tariff block |
| 09:30 | 715 | On-Peak | Short production surge |
| 09:45 | 750 | On-Peak | Measured monthly peak interval |
Formula Used
1) Ratchet Demand
Ratchet Demand = Annual Peak Reference × Ratchet Percentage
2) Adjusted Measured Peak
Adjusted Measured Peak = Measured Peak × (1 + Loss Factor%)
3) Base Billed Demand
Base Billed Demand = max(Adjusted Measured Peak, Ratchet Demand, Minimum Billed Demand)
4) Power Factor Multiplier
If Actual PF < Target PF, Multiplier = Target PF ÷ Actual PF. Otherwise Multiplier = 1.
5) Final Billed Demand
Final Billed Demand = Base Billed Demand × Power Factor Multiplier
6) Excess Contract Demand
Excess Demand = max(0, Final Billed Demand − Contract Demand)
7) Total Demand Charges
Total = Facility Charge + On-Peak Charge + Mid-Peak Charge + Excess Penalty + Fixed Charge
This structure fits many manufacturing tariffs where the highest valid demand, tariff period peaks, and contract overruns all affect the final invoice.
How to Use This Calculator
Step 1: Enter the measured monthly peak demand or paste interval demand values.
Step 2: Add tariff-specific fields such as contract demand, ratchet percent, minimum billed demand, and demand rates.
Step 3: Add actual and target power factor values if your utility adjusts demand for low power factor.
Step 4: Include loss factor, fixed charge, and any excess demand penalty rate used by your tariff.
Step 5: Optionally enter operating hours and monthly production units for cost-per-hour and cost-per-unit insight.
Step 6: Click Calculate Demand Charges to see the result above the form, review the chart, and export CSV or PDF.
Frequently Asked Questions
1) What is a peak demand charge?
A peak demand charge is the part of an electricity bill based on the highest rate of power used during a billing period. Utilities apply it because short spikes force them to maintain generation, network, and transformer capacity even if average energy use stays moderate.
2) Why does ratchet demand matter?
Ratchet demand matters because some tariffs bill a percentage of your prior highest demand even when the current month is lower. It protects utility revenue and can keep charges elevated for months after one unusual production spike.
3) How does power factor affect demand charges?
Low power factor can increase billed demand because utilities may scale demand upward when your plant uses reactive power inefficiently. Improving motor correction, capacitor banks, and load management can reduce this multiplier and lower the final invoice.
4) Should I use interval data or one monthly peak number?
Interval data is better when available because it reveals when spikes occur and gives a more useful chart. A single monthly peak is still enough for quick estimation, but it hides load timing and improvement opportunities.
5) What does contract demand penalty mean?
A contract demand penalty applies when your billed demand exceeds the capacity level agreed in the utility contract. It signals that the facility is using more grid capacity than reserved and may justify renegotiation or operational controls.
6) Can this calculator help with production planning?
Yes. It helps compare scenarios before changing shifts, sequencing large motors, or adding new equipment. The cost-per-hour and cost-per-unit metrics are especially useful when finance and operations need one shared demand-cost view.
7) What is the difference between energy charges and demand charges?
Energy charges depend on how many kilowatt-hours you consume. Demand charges depend on how fast power is drawn at the highest interval. A facility can lower demand charges even when total monthly energy use changes very little.
8) How can a factory reduce peak demand charges?
Factories often reduce demand charges by staggering equipment starts, shifting noncritical loads, improving power factor, using storage, limiting simultaneous heavy processes, and monitoring interval demand in real time before peaks become billable.