Do Power Quality Devices Save Energy?

There are many suppliers that promote energy savings associated with their products of up to 20 percent or more. This sounds like is a substantial benefit, and if you are considering investing in power factor devices, it is important to understand the basis of these energy-saving claims, because they do not apply to all electricity users.  In fact, they don’t apply to most users.

Understanding power factor

Power quality devices that improve power factor can reduce your overall electric bill, while providing little or no energy savings. How is this possible? To answer this question, you must understand the concept of power factor and the difference between active power, reactive power and apparent power.

All electrical equipment requires power to do work; this is called active power and it is measured in kilowatts (kW). Some equipment, such as induction motors or transformers, requires additional power to create the magnetic field needed to operate the device. This is known as reactive power and is measured in kilovar (kVAR). Apparent power, measured in kilovolt-amps (kVA), is the total amount of power supplied (the combination of active power and reactive power). Power factor is the percentage ratio of active power over apparent power. It is demonstrated in the phase relationship between voltage and current; if current leads or lags voltage, power factor is poor.

While power factor is a difficult concept to understand, the important thing to remember is whether your electric bill includes a penalty for power factor. This is because facilities with low power factor draw more kVA, requiring additional generation capacity.

Power factor correction devices, such as capacitors and harmonic filters, can significantly reduce reactive power and improve your power factor rating, but they will have little or no effect on kW power demand or kWh energy use. If your utility charges for low power factor, you can save anywhere from 10 to 30 percent on your this portion of your electric bill, but the actual energy savings from power factor correction is typically much less than 5 percent. (Carnovale 2010)  If your utility does not charge a penalty for a low power factor, these devices will save you absolutely nothing.  If you do have a penalty, remember that the savings percentage only applies to the penalty fee, not your kWH usage.  Most marketers of this equipment do not explain this, unless you are working with a supplier that has the instruments, and the engineer to use them to measure the power factor of your electrical load.  If they don’t, then you will likely be very disappointed.  Power factor correction equipment must be customized to the specific customer.  It is not an out-of-the-box solution that you simply plug in. Don’t be fooled!  Their greatest benefit relate to induction motor devices.

Do your homework

There are opportunities to save money by applying power quality solutions. Power quality devices protect critical equipment, reducing downtime and saving on maintenance and repair costs. In many facilities, power quality devices can improve power factor and reduce utility penalties. While power quality devices can provide a small amount of energy savings in some cases, the energy-saving claims made by some power quality solutions providers are often overblown. It is important to do your homework and carefully investigate any energy-saving claims made by manufacturers before you invest in a power quality solution for your facility.

References

Carnovale, Daniel. “The Truth Behind PQ Solutions and Energy Savings.” Electrical Construction & Maintenance. March 1, 2010.

Electric Power Research Institute (EPRI). Power Quality Guidelines for Energy-Efficient Design Applications. Prepared for the California Energy Commission. January 2003.

Energy Savings Claims from Power Conditioning Equipment