Consult your local electrical code (e.g., Table A1 in BS 7671) for diversity guidelines.
Several subtleties often trip up practitioners. First, : A single consumer’s MD is non-coincident (their own highest interval). But the utility’s system peak is coincident—when all consumers happen to be high simultaneously. A consumer who shifts load away from the system peak reduces both their own MD and the utility’s stress.
The maximum power actually used at any one time, which is usually lower than the connected load because not all appliances run simultaneously. Why Perform Maximum Demand Calculation? Accurate calculation is essential for:
For existing installations, actual metered data provides the most accurate maximum demand determination. This data should be averaged over appropriate demand intervals to eliminate transient effects. maximum demand calculation
For utility billing purposes, the measurement period is generally one month, though demand intervals of 5, 15, 30, or 60 minutes are also used depending on the application. A standard contract clause defines maximum demand as "the highest 30-minute integrated demand created during the current billing month".
Here is a practical breakdown of how a maximum demand calculation is structured for a small commercial space. Load Category Connected Load (VA) Code Diversity Factor Calculated Maximum Demand (VA) 0.90 (90%) Power Outlets 0.50 (50%) Air Conditioning 1.00 (100% Interlocked) Kitchenette Appliances 0.30 (30%) Total Demand 68,000 VA N/A 51,400 VA Final Step: Determining Service Amperage
Used primarily for complex industrial or commercial sites. Engineers analyze the specific operational duty cycles of machines, interlocking mechanisms (where two machines cannot run at once), and known base loads to assess peak demand. 3. Calculation by Measurement Consult your local electrical code (e
Total connected load = 100 + 200 + 50 + 50 = 400 kW
Failing to account for future electric vehicle (EV) chargers or solar battery integration.
Time-of-use and differential demand metering also affects billing. In some jurisdictions, the measured kW demand is the greater of the maximum kW demand in the on-peak period or 25% of the maximum kW demand during the off-peak period. But the utility’s system peak is coincident—when all
The sum total of the continuous power ratings of all electrical appliances, fixtures, and machinery installed within a facility. It represents the power consumed if every single device were turned on and operating at full capacity simultaneously.
is defined as the highest amount of power (typically measured in kilowatts, , or kilovolt-amperes, kVAk cap V cap A
Typically calculated by total wattage or VA, categorized by luminaire type (LED, fluorescent, HID).