HVAC Variable Speed Drive

Approximately half of the electricity in commercial buildings is used to move air and water around. Motor driven components used in HVAC are the highest energy consumer in the commercial sector. Using variable speed drives (VSDs) within HVAC systems saves energy and money.


Most HVAC systems are designed to operate fans and pumps at a constant speed for peak load. This means the HVAC system is typically oversized during the majority of operating hours for most applications. VSDs, also referred to as variable frequency drives (VFDs), are capable of varying the output speed of a motor to meet the demand of the system. VSDs match the amount of work or load on a motor to the amount of energy that is required, reducing energy use. VSDs also have built-in soft start capability, which extends the life of the motor.


Incentives are available for new equipment installations through Idaho Power’s Commercial and Industrial Energy Efficiency Program. An incentive of $125 per hp is available for installing a VSD/VFD on chilled water pumps, condenser water pumps, cooling tower fans, supply, return, outside air, make-up air fans and hot water pumps.

To qualify, VSD/VFD must be installed on variably-loaded electric motors, that are not required by code for new construction. The motors must be less than 300 hp and operate at least 2,000 hours per year, some exceptions may apply. All VSD/VFD installations must comply with Idaho Power’s Rule K “Practices and Requirements for Harmonic Control.”


Costs vary depending on the size of motor and how often the fan operates annually. The payback period, including incentives, is typically between six months and two years.