Fan motor saving at equal efficiency calculator

Use this shortcut only when the compared motor efficiencies match.

Units

\Delta \mathrm{kW} = \frac{\left(\mathrm{HP}_{\text{old}} - \mathrm{HP}_{\text{new}}\right) \times 0.746}{\eta}

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

\Delta \mathrm{kW} = \frac{\left(30 - 18\right) \times 0.746}{0.9} \approx 9.947

Symbol	Meaning	Unit
$\Delta \mathrm{kW}$	electric input reduction	kW
$\mathrm{HP}_{\text{old}}$	old actual shaft requirement	HP
$\mathrm{HP}_{\text{new}}$	new actual shaft requirement	HP
$\eta$	common motor efficiency	—

Symbol	Meaning	Unit
$\Delta \mathrm{kW}$	electric input reduction	kW
$P_{\text{shaft,old}}$	old actual shaft requirement	kW
$P_{\text{shaft,new}}$	new actual shaft requirement	kW
$\eta$	common motor efficiency	—

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.