from Maria in Madison, WI:
#359
I manage the facilities of a small industrial company. A vendor recently approached me with a black box device that hooks up to either my motors or to my main electric supply panel and is supposed to reduce amp draw by 15-20%. This seems too good to be true, will I really save energy?
You likely won’t see a reduction at the electric meter.
Will your amperage be reduced? Yes. But more importantly, will you save energy? Probably not. It sounds like this vendor is selling one of many varieties of power conditioning or power factor correcting devices. Inductive loads such as lightly loaded electric motors often have a low power factor. A low power factor means that not all of the amps drawn by your facility are actually used to do work. You might say that some of the amperage is "returned" to the power plant without being used. These black box devices usually contain capacitors that can improve the power factor, reducing the amperage measured. However, this does not mean that electrical energy (kWh) or demand (kW) as measured and billed by your electric utility company has been reduced (meaning you won’t reduce your energy bill). When a power factor correcting device is installed, the power factor is increased, amps go down, but the "true" kW stays about the same, so you probably won’t see any reduction at the electric meter. Some utilities charge for having a poor power factor, in that case, the black box device may help lower this fee (check with your utility), but from an energy savings standpoint there is little to no benefit.
The same applies for residential customers. A power factor correcting device can be found and purchased on the internet and may claim to reduce your energy bills. Like in commercial installations, the box usually is installed near the main electrical box and can improve power factor but won’t reduce your energy use or your bill.
For more information on power factor correcting devices and what energy experts have to say, check out these resources: