VFD Energy Savings Calculator
Estimate energy and cost savings by implementing Variable Frequency Drives
VFD Energy Savings Calculator
Optimize your motor's energy consumption
Results:
Daily Energy Savings (kWh): 0.00
Daily Cost Savings ($): 0.00
Monthly Energy Savings (kWh): 0.00
Monthly Cost Savings ($): 0.00
Annual Energy Savings (kWh): 0.00
Annual Cost Savings ($): 0.00
Power Reduction (%): 0.00
How to Use the Calculator
Input Motor Details
- Enter the motor's rated power in kilowatts (kW).
- Specify the daily operating hours for the motor.
- Input the number of operating days per year.
Energy Cost & Frequencies
- Provide your local energy cost per kilowatt-hour ($/kWh).
- Enter the motor's current operating frequency (Hz).
- Input the desired reduced operating frequency (Hz) with VFD.
Calculate & Analyze
- Click "Calculate Savings" to see results.
- View estimated annual energy and cost savings.
- Understand the percentage of power reduction achieved.
VFD Energy Savings Fundamentals
Affinity Laws
VFDs save energy by reducing motor speed, which significantly reduces power consumption for centrifugal loads (pumps, fans). This relationship is governed by the affinity laws:
- Flow is proportional to speed.
- Pressure is proportional to the square of speed.
- Power is proportional to the cube of speed.
VFD Benefits
- Significant energy cost reduction.
- Improved process control and stability.
- Reduced mechanical stress on equipment.
- Lower maintenance costs and extended equipment life.
Key Formula for Power Reduction:
Preduced = Poriginal × (freduced / foriginal)3
Annual Cost Savings:
Savings = (Poriginal - Preduced) × Operating Hours × Cost/kWh
Calculation Formulas
Power Reduction Ratio:
Ratio = (freduced / foriginal)3
Reduced Power (kW):
Preduced = Poriginal × Ratio
Annual Energy Savings (kWh):
Esavings = (Poriginal - Preduced) × Hours/Year
Annual Cost Savings ($):
Csavings = Esavings × Cost/kWh
Example Calculation
Consider a 10 kW motor operating 12 hours/day, 300 days/year, with an energy cost of $0.15/kWh. If the frequency is reduced from 60 Hz to 45 Hz:
Poriginal = 10 kW
foriginal = 60 Hz, freduced = 45 Hz
Ratio = (45 / 60)3 = (0.75)3 = 0.421875
Preduced = 10 kW × 0.421875 = 4.21875 kW
Power Savings = 10 - 4.21875 = 5.78125 kW
Annual Operating Hours = 12 hours/day × 300 days/year = 3600 hours/year
Annual Energy Savings = 5.78125 kW × 3600 hours = 20812.5 kWh
Annual Cost Savings = 20812.5 kWh × $0.15/kWh = $3121.88
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