Fitting a variable-speed drive to control an HVAC fan or pump motor will often result in substantial cost savings.
Just how substantial these are can be calculated using a free CD, available from Trend Control Systems.
Once the user has entered the power of the motor, its running hours and the price paid per kWh, the calculator reveals how much money is saved for a given reduction in motor speed. Using this figure, plus typical costs for installation and commissioning the variable speed drive, it then also calculates the payback period.
Source
Building Sustainable Design
