: Uses terms like "factor of maximum utilization (ku)" and "factor of simultaneity (ks)" for similar purposes
Understanding Maximum Demand Calculation: A Comprehensive Guide for Electrical Systems
Because diversity factor is the reciprocal of coincidence factor, it is typically greater than 1, reflecting the reality that not all loads peak at the same time. The higher the diversity factor, the greater the spread in load usage times, which allows for more efficient system design.
: The minimum unit load (including most receptacles and lights) should not be less than 3VA per square foot, which can then be reduced as permitted maximum demand calculation
If you need to calculate this for a specific project, let me know:
Maximum demand is the starting point for transformer sizing. The general approach follows these steps:
: A common thumb rule is to take 100% of the largest circuit's rating and 40% of all remaining circuits. : Uses terms like "factor of maximum utilization
Multiply the total wattage of each specific category by its designated demand factor. These factors are standard constants sourced from local regulatory codes (e.g., National Electrical Code or BS 7671). Step 3: Account for the Diversity Factor
For the , MD is the basis for demand charges, often the largest component of an industrial electricity bill. A typical commercial tariff might charge $10 per kW of MD plus $0.10 per kWh. A factory with an MD of 1000 kW thus pays $10,000 in demand charges before any energy charges. Reducing MD by just 100 kW through load shedding or power factor correction saves $1,000 monthly—a powerful incentive.
In an era of variable renewable energy, electric vehicles, and dynamic tariffs, maximum demand calculation is no longer a static “set and forget” design task. It is an ongoing process of monitoring, verification, and adjustment—but the fundamental principles laid out in this article provide the foundation that every electrical engineer, facility manager, and energy consultant must master. The general approach follows these steps: : A
Utilities do not charge for a lightning-fast surge (e.g., starting a 200kW motor for 2 seconds). Instead, they measure the sustained load over a sliding window. If your load peaks for 5 minutes and drops to zero, the 30-minute average will be modest. However, if you sustain high load for the entire window, your MD spikes.
Even experienced engineers fall into recurring traps when calculating maximum demand.