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Calculation Machine

VFD Energy Cost Savings Calculator

Annual dollar savings from adding a VFD to a fan.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Annual energy saved
52,031 kWh
Annual cost savings
$6764
New average power
6.33 kW
Percent power saved
57.8%

Quick answer

Annual savings equal the power reduction at reduced speed times annual run hours times the electricity rate.

The formula

Savings = (P1 - P1 x (N2/N1)^3) x hours x rate

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Full-speed power15 kW
  • Average VFD speed75 % of full speed
  • Annual run hours6000 hr
  • Electricity rate0.13 $/kWh

Result

  • Annual energy saved52,031 kWh
  • Annual cost savings$6764
  • New average power6.33 kW
  • Percent power saved57.8%

How to use the VFD Energy Cost Savings Calculator

  1. 1Enter the fan's full-speed power draw and the average speed it will run at with a VFD.
  2. 2Enter annual operating hours and your electricity rate.
  3. 3Read the annual energy and cost savings to help justify the VFD payback.

Frequently asked questions

How do I find average VFD speed?

Use trend logs from an existing BAS, or estimate from typical load profiles for the application.

Does this include drive losses?

No — VFD and motor conversion losses are small (a few percent) and can be added as a simple derate if needed.

About this calculator