VFD Energy Savings & Payback Calculator
Compute electrical kilowatt reduction, annual kWh savings, and simple payback period for VFD retrofits on centrifugal pumps and fans using affinity cubic laws.
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Frequently Asked Questions
Why does reducing motor speed save so much more energy than throttling a valve?
A throttling valve restricts flow by deliberately introducing artificial friction resistance, dissipating pressure as heat while the pump motor continues running near full power. In contrast, a VFD slows the pump itself; by the cubic affinity law, a 20% speed reduction cuts motor power demand by nearly 50% (0.80³ = 0.512).
What is typical simple payback period for an industrial VFD installation?
For pumps and fans operating continuously (> 5,000 hours/year) with variable flow demands between 50% and 80%, simple payback is typically between 9 and 24 months, with utility efficiency rebates frequently reducing payback to under 12 months.
Does a VFD introduce any electrical losses?
Modern IGBT-based variable frequency drives operate at 96% to 98% electrical efficiency. The 2% to 4% heat dissipation in the drive cabinet is dwarfed by the 30% to 60% energy savings achieved at the motor shaft.