In the world of commercial and industrial electricity billing, "Demand Rate" is one of the most critical components of your utility bill. Unlike residential bills that primarily focus on total energy consumption (kWh), industrial bills include a "Demand Charge" based on the maximum amount of power you require at any single point in time.
What is Demand Rate?
The Demand Rate is the price your utility company charges per kilowatt (kW) of peak power used during a billing cycle. While Energy is the total volume of electricity used over time, Demand represents the speed at which you use it. Think of it like a car: Energy (kWh) is the distance traveled, while Demand (kW) is the maximum speed reached during the trip.
The Demand Rate Formula
To calculate various aspects of demand, we use three primary formulas:
Average Demand (kW): Total Energy (kWh) / Total Hours in Period (h)
Load Factor (%): (Average Demand / Peak Demand) x 100
Demand Charge ($): Peak Demand (kW) x Rate per kW ($/kW)
Step-by-Step Example
Suppose a small manufacturing facility consumes 10,000 kWh in a 30-day month (720 hours). During that month, their highest recorded 15-minute power spike was 40 kW. The utility charges a demand rate of $15.00 per kW.
Average Demand: 10,000 kWh / 720 hours = 13.89 kW
Demand Charge: 40 kW x $15.00 = $600.00
Load Factor: (13.89 / 40) x 100 = 34.7%
Why Demand Rates Matter
Metric
Importance
Peak Demand (kW)
Determines the infrastructure the utility must maintain for your site.
Load Factor
A higher percentage indicates more efficient, steady energy usage.
Demand Charge
Can often account for 30% to 70% of a total commercial electric bill.
Tips to Lower Your Demand Rate Charges
To reduce your bill, you must "level out" your consumption. This is known as peak shaving. You can achieve this by:
Staggering Equipment Starts: Avoid turning on all large motors or HVAC units at the same time.
Battery Storage: Use stored energy during peak periods to lower the pull from the grid.
Operational Scheduling: Move high-energy processes to off-peak hours when the peak demand calculation might be lower or ignored.