Estimate your potential energy savings

5-step savings estimator from Yaskawa Electric shows how to compare variable frequency drive performance savings to other methods of motor volume control. Now includes downloadable calculator!


Industrial Calculator

Much has been written in the pages of Control Engineering about the use of variable frequency drives to save energy . This content has often focused on how VFDs enable energy savings via their namesake partial operating modes versus regular drives' all-on or totally-off method of operation.

What's been missing from much of this discussion is how to figure out how much money the use of a VFD could possible save your particular operation. Now, with the help of a simple-to-follow,

All you need to perform the calculations is your current motor:

  • Horsepower;

  • Cost per kWh of electricity;

  • Total hours of operation per year (8,760 maximum); and

  • Thealternative to VFD control (inlet guide vane, outlet damper, ride thefan curve, discharge valve, bypass damper, bypass valve or no control).

Here are the 5 steps: Annual VFD Estimated Savings Calculator

(Theresult here is your estimated annual savings using a VFD. This resultis only an estimate based on averages and assumptions. You should alsoconsider additional savings to be gained from VFD application over andabove the electricity rate, such as power factor improvement to 0.98and reduced demand charges. )

Step 1. Convert motor hp to kW:

___________HP × .746 = _______ kW1

Step 2. Multiply the Variable Frequency Drive Power Ratio (from Table below) times kW1 from Step 1:

______Ratio × ______kW1 = ______ kW2 (using VFD)

Step 3. Multiply the power ratio of the control method now being used (see table below) times kW1 from Step 1:

______ Ratio × ______ kW1 = ______ kW3 (method now being used)

Step 4. Subtract Step2 kW2 from Step 3 kW3:

______ kW3 minus ______ kW2 = ______ kW4 (savings using VFD)

Step 5. Multiply Step 4 kW4 savings times hours per year of operation times cost per kWh of electricity:

____ kW4 × ______ Hrs × $______/kWh = $______

Pumps at 70% of maximum flow*


Flow control method


Variable Frequency Drive


Discharge valve


Bypass value


No Control

Fans at 60% of maximum flow*


Flow control method


Variable Frequency Drive


Inlet Guide vane


Outlet Damper


Ride the Fan Curve


Bypass Damper

* The power ratio data in the above tables is a conservative assumption based on HVAC applications which have shown that fans and pumps operate, on average, at 60% and 70% of maximum flow rate, respectively.

To help illustrate how this savings estimator works before you conduct your first test, see this example:

Basedon a 60 hp fan motor operating 24 hours per day (or 8,760 hours peryear) riding the fan curve for variable volume control and the localutility charges $0.12 per KwHr:

  • Step 1.) 60 hp × .746 = 44.76 kW1

  • Step 2.) .32 Ratio × 44.76 kW1 = 14.32 kW2

  • Step 3.) .94 Ratio × 44.76 kW1 = 39.39 kW3

  • Step 4.) 42.07 kW3 - 14.32 kW2 = 27.75 kW4

  • Step 5.) 27.75 kW4 × 8,760 hrs × $0.12/kWh = $29.172 annual savings...for one motor!

Nowyou can download an Excel version of this calculator to perform thesecalculations more quickly and easily by clicking on this link: VFD Savings Calculator .Fields that require input include Excel notes as reminders of what datashould be placed in the field. Our thanks to Jerry Archer of JacobsEngineering for providing us with this helpful resource.


- By David Greenfield , editorial director, with data from Yaskawa Electric America
Control Engineering Sustainable Engineering
News Desk

No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Integrated mobility; Artificial intelligence; Predictive motion control; Sensors and control system inputs; Asset Management; Cybersecurity
Big Data and IIoT value; Monitoring Big Data; Robotics safety standards and programming; Learning about PID
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Big Data and bigger solutions; Tablet technologies; SCADA developments
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me