Maximum Demand Calculation Page

Pro Tip: Do not trust one day of data. A single anomaly (testing a backup generator, a heatwave) could set an unrealistic MD.

Install a demand meter (digital kWh meter with demand register) or power analyzer.

How it works:

Example (30-min block):

If you already applied a 0.5 demand factor to receptacles (knowing only half are used), and then apply a 0.8 diversity factor, you are double-penalizing. Demand factors apply to groups; diversity applies between groups.

Numerical example: 15‑min averages [120, 150, 200, 180] kW → MD = 200 kW. If PF = 0.9, MD_kVA = 200/0.9 ≈ 222.2 kVA.

There are three primary approaches: the Manual Diversity Method, the Historical Data Method, and the Load Survey Method. maximum demand calculation

Used when designing a new installation. You sum all connected loads, then apply demand factors and diversity factors.

Formula: [ MD = \textSum of Individual Loads \times \textDemand Factor \times \textDiversity Factor ]

[ kVA = \frackWPower\ Factor ]

Assume PF = 0.85:
( 18.58 / 0.85 = 21.86 \ \textkVA ) → Round to 25 kVA transformer.

Standards like IEEE 141 (Red Book), IEC 60364, and the National Electrical Code (NEC) Article 220 mandate specific demand factors for load calculations to prevent overloads.