Peak Demand

Free Peak Demand calculator with clear step-by-step results.

About Peak Demand

Connected load is never all running at once. A demand factor reduces it to what each load actually draws, a diversity factor accounts for loads peaking at different times, and dividing by power factor converts real power into the apparent power that transformers, cables and tariffs are all sized on.

Formulas

Maximum demand

kW = connected load x demand factor / diversity factor

Apparent power and current

kVA = kW / power factor; three-phase amps = kVA x 1000 / (V x root 3)

Worked example

With the default values below, Peak Demand returns Maximum demand of 66.67. Change any input above and every figure here is recalculated in your browser.

Inputs used

Total connected loadminimum 0.1 kW: 120 kW
Demand factoraccepts 5–100 %: 65 %
Diversity factoraccepts 1–4: 1.3
Power factoraccepts 0.3–1: 0.9
Supply voltage (line to line)minimum 100 V: 400 V
Demand chargeminimum 0 $/kVA/month: 12 $/kVA/month

Results

Maximum demand: 66.67 kVA
Maximum demand in real power: 60.00 kW
Three-phase line current: 96.2 A
Monthly demand charge: $800.00

Step by step

1Values used
2Maximum demand
3Apparent power and current
4Maximum demand= 66.67 kVA
5Maximum demand in real power= 60.00 kW
6Three-phase line current= 96.2 A
7Monthly demand charge= $800.00

Assumptions and limits

The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Maximum demand assessment for supply sizing must follow the applicable wiring regulations and utility connection rules. Have the design verified by a qualified electrical engineer.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Maximum demand assessment for supply sizing must follow the applicable wiring regulations and utility connection rules. Have the design verified by a qualified electrical engineer.

Frequently Asked Questions

Why is billing based on kVA rather than kW?

Because network equipment must carry the apparent current, including the reactive component that does no useful work. Poor power factor raises kVA without raising kWh, which is why correction pays for itself.

What demand factor should I use?

It depends on load type - lighting can be near 100%, motor groups often 50-70%, and welding or intermittent plant far lower. Metered history is far better than a rule of thumb.