What the calculator does
It splits one electric bill into demand and energy, so you can see how much your single highest peak set.
How each result is worked out
An NREL analysis of more than 10,000 utility tariffs found demand charges “can account for anywhere from 30% to 70% of a customer’s electricity bill” (National Renewable Energy Laboratory, 2017).
- Demand cost is your peak demand in kW times the demand charge per kW. NREL explains the peak is typically the highest average use in one interval, usually 15 minutes.
- Energy cost is the kWh used in the period times the energy charge per kWh.
- Total is demand cost plus energy cost plus the fixed monthly customer charge.
- Demand share is demand cost divided by the total.
- Load factor is the kWh used divided by what the peak would have used running every hour of the period: peak kW times days times 24. A low load factor means short, sharp peaks.
- Each 10 kW of peak is 10 times the demand charge: how much this bill moves if the peak is 10 kW higher or lower.
Real bills add riders, taxes, time-of-use periods, ratchets and minimums, so treat the result as an estimate of this one bill. Take the charges from your own bill or the current rate schedule; the bill anatomy guide shows where each one sits.
Calculator questions, answered
Where do we find the demand charge per kW?
On the bill, beside the demand line, or in the rate schedule the bill names. The bill usually shows billed kW and a dollar amount; dividing the dollars by the billed kW gives the price per kW for that month. If the tariff has seasonal or tiered demand prices, use the one that applied to that bill.
What is a good load factor?
There is no single good number, because it depends on what the building does. A warehouse running one shift will sit lower than a cold storage site running around the clock. The trend matters more: a falling load factor at the same site usually means sharper peaks, and those show up in the demand charge.
Will cutting 10 kW of peak cut the bill by the amount shown?
Only on a simple schedule. Many tariffs carry ratchets, minimum demand, seasonal prices or time-of-use demand windows, and some riders are priced per kW too. The calculator shows the direct demand charge effect on one bill. Our Demand Charge Plan models those rules on 12 months of interval data for one site.
Is anything we enter saved or sent?
No. The calculator runs entirely in your browser: the numbers stay on your device and disappear when you reload or close the page. We do not log inputs, and the site sets no tracking cookies. If you want an analyst to look at the real bill, send it through the free Three-Bill Read instead.
Find out what set your peak
A Demand Charge Plan reads 12 months of interval data for one site, from $3,200.