"Power Factor" can significantly affect costs for electric service. Understanding and improving your power factor is important and should be a component of your energy management plan.
What Is Power Factor?
Power factor is a term that expresses the relationship between working
power the power actually consumed at your business and the capacity which
must be supplied by us to have this working power available.
Working power is expressed in kilowatts or kW (one kilowatt = 1,000 watts). This registers as kilowatt-hours on your electric meter. The total capacity required is expressed in kilovolt-amperes, or kVA (Electrical equipment such as generators and transformers is rated in kVA).
Power factor is the ratio of the working power to the total capacity required to provide this power or kW/kVA.
Why Is Power Factor Important?
Power factor can impact your energy costs. Improving the power factor can
improve efficiency, often resulting in significant economic savings.
Benefits of Improving Power Factor
- Reduced energy costs
- Lower transmission and distribution losses in your electrical system
- Higher and more quality voltage regulation
- Increased capacity available to serve actual working power requirements
- Reduced non-productive loading on the system
How Does Power Factor Affect Electric Bills?
There is a substantial cost increase in serving customers with low power factor
loads. These costs are not reflected in metered use of working power.
Therefore, special provisions are made to compensate Detroit Edison for the
additional investment. Accordingly, some Detroit Edison rates call for
penalties ranging from 1 to 3 percent when the power factor is between 85 and
70 percent.
Power factors below 70 percent are not permitted, and customers are required to invest in corrective equipment necessary to improve the power factor above this level. Until corrections are made a 25 percent penalty charge will be applied to any billing after two consecutive months below 70 percent power factor and will continue as long as the power factor remains below this level.
Below are examples of how power factor affects your monthly electric bill.
For a mid-size Primary Service Customer:
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For a large-size Primary Service Customer:
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What Kind of Loads Contribute to Poor Power Factor?
- Lightly loaded or oversized motors or transformers
- Most welding operations
- Certain fluorescent lamp ballasts
What Can Be Done to Improve Power Factor?
The best way to improve your power factor depends largely on the particular
operating considerations involved. In some cases, motors or transformers can be
sized more closely to the actual work requirement, effectively improving the
power factor. It may be that motor idling or "no load" running periods
can be reduced, with a two-fold benefit-improved power factor and more
effective energy management.
In extreme cases, where power factor is below 85 percent, customers may be required to invest in corrective equipment. Detroit Edison can provide you with a listing of qualified equipment vendors to complete the installations.
For more information on how to improve your power factor contact your account manager. Our engineers are qualified and always available to discuss specific recommendations with you.
