Peak demand explained
Peak demand is the highest average power you draw over one billing interval. It is an average over the interval, so very short spikes are smoothed, while longer ones are not.
Averaging within the interval
Suppose the interval is 15 minutes. A site runs at 300 kW, but for 2 of those minutes a start-up pulls 800 kW.
| 2 minutes at 800 kW | 1,600 kW-minutes |
| 13 minutes at 300 kW | 3,900 kW-minutes |
| Interval average: 5,500 / 15 | 367 kW |
The spike lifts the interval from 300 kW to about 367 kW. If the same start-up ran for the full 15 minutes, the interval would read 800 kW. That is why interval length matters and why you should check yours.
Why it matters
Billed demand is usually the highest such interval in the month. Finding it takes interval data, not a monthly total.
Frequently asked questions
Is peak demand the same as the highest instant of power?
No. It is the highest interval average, so a very brief spike counts only partly.
What data do I need?
Interval data, such as 15-minute readings, from your utility or meter.
Does peak demand include time-of-use windows?
Some tariffs bill separate peaks for on-peak hours. Check your rate schedule.
Try it on your own numbers
All numbers on this page are illustrative, including the rate. They are not a real utility tariff. Your bill depends on your utility rate schedule; check it before acting. Peak Ledger gives estimates, not a utility bill or an engineering design.