VFD Energy Savings Chart

Use this worksheet after the calculator result to record motor power, load type, load factor, speed reduction, runtime, kWh savings, demand savings, maintenance savings, and payback.

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Quick reference table

A VFD energy savings chart is a calculator-led planning worksheet. It keeps the motor and load assumptions behind a VFD savings result visible before equipment selection or project approval.

VFD savings worksheet

VFD savings worksheet
Item	Record from calculator	Follow-up
Motor	Power, voltage, efficiency	Confirm nameplate and duty
Load	Fan, pump, conveyor, or other type	Check whether speed reduction is realistic
Savings	kWh, demand, and maintenance savings	Separate measured and assumed values
Project	VFD cost and payback	Review harmonics, bypass, controls, and commissioning

VFD application review lanes

VFD application review lanes
Application item	Record on worksheet	Why it changes savings
Fan or pump affinity case	Speed profile, minimum speed, control mode	Affinity-law savings depend on real speed reduction
Constant-torque load	Process limit, torque demand, duty note	The savings model may not follow a cubic speed relationship
Bypass or manual mode	Bypass use, operator override, hours excluded	Bypass time can erase expected savings
Commissioning check	Control sequence, setpoints, measured kW	Verified operation is needed before claiming savings

Formula basis

Variable-torque power screen: power ratio is approximately speed ratio cubed.

Motor power is the rated motor kW or HP used by the calculator.
Load type identifies whether the affinity-law estimate is appropriate.
Speed reduction is the average operating speed change entered for the screen.
Annual savings includes energy, demand, and maintenance items entered in the calculator.

Worked examples

Pump VFD savings recordRecord motor kW, variable-torque load type, speed reduction, operating hours, rate, annual savings, VFD cost, payback, and commissioning follow-up.

Air-handler fan turndown recordKeep fan HP, average speed schedule, occupied hours, static-pressure control note, bypass status, annual kWh savings, and commissioning measurement in one review package.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

VFD savings depend on the real load profile, control strategy, minimum speed, process requirements, and commissioning.
The worksheet does not select a drive package or prove utility savings by itself.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Use this chart as a comparison worksheet; verify motor nameplate data, drive manufacturer requirements, utility rate and demand charges, harmonic and bypass needs, owner process constraints, and commissioning data before approval.

How to use this chart

1Anchor to motor dataRecord motor rating, voltage, efficiency, and duty before reviewing savings.

2Document the load profileWrite load type, average speed reduction, runtime, and process constraints.

3Route commissioning checksUse the chart to list controls, harmonics, bypass, and measured-savings follow-up.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Capture motor inputsRecord motor power, efficiency, voltage, load factor, and operating hours.
Capture savingsDocument kWh, demand, maintenance savings, project cost, and payback.
Capture follow-upList drive selection, harmonic review, control sequence, and measurement plan.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Applying variable-torque assumptions to a load that cannot reduce speed.
Ignoring demand charges, bypass needs, or commissioning when presenting savings.
Quoting VFD payback without documenting the load profile, minimum speed, control sequence, and measured post-startup kW.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Do all VFD projects save energy?

No. Savings depend on load type and speed reduction. Constant-torque loads and limited speed changes may produce different results.

Why record load type?

Fan and pump affinity-law screening does not apply the same way to every motor-driven load.