A client is asking whether installing variable frequency drives on their HVAC motors would reduce their demand charges enough to justify the cost. I'm an auditor not an engineer — should I be making equipment recommendations? And does anyone have real-world data on demand reduction from VFDs?
VFDs — demand savings vs maintenance headaches
I don't recommend specific equipment but I do quantify the potential savings from demand reduction so the client can make an informed decision. For VFDs specifically, the demand reduction depends on the motor size and the load profile. On a 50 HP supply fan motor that's currently running at full speed, a VFD might reduce average demand by 30-40% during partial load conditions. Whether that justifies a $15-20K investment depends on the client's demand rate and how many hours the motor runs at partial load.
I agree with Derek — quantify the savings opportunity but let the client and their mechanical engineer decide on the equipment. Your role is to identify that demand charges are higher than they need to be and to estimate what the demand charges would be at various reduced levels. The client takes that information to their engineer who recommends the specific solution. This keeps you in your lane as a billing expert while still delivering actionable value.
Perfect — I'll stick to quantifying the demand charge savings at different demand levels and let the engineer handle the equipment side. Thanks for clarifying my role.