EET

Why power factor correctors for the home don't really work

A team of National Institute of Standards and Technology (NIST) researchers recently put out a white paper explaining why power factor correction type devices actually provide no savings to consumers.

The devices—sometimes referred to as Amp Reduction Units or KVARs—are touted as good investments because they reduce the amount of current drawn from power lines while simultaneously providing enough current for appliances.

“One of the important functions of our primer is to remove the mystery of how current from the power line can decrease while at the same time current going to an appliance remains the same,” says NIST researcher Martin Misakian. The Note shows that the devices can indeed reduce current flow from the power line. But it is not just the current flowing from the power line that determines your electric bill, but the product of the power factor and the current. Though current decreases with a power factor correction device, the power factor rises correspondingly, meaning the product of the two remains the same—with or without the device. Because a residential electric bill is proportional to this product, the cost remains unchanged.

Ironically, though power factor correction devices won't reduce the average homeowner’s bill, they may benefit the utility which would need to supply less reactive power to a residence.

But while the primer does provide a rough calculation of a utility’s savings by considering the operation of a residential air conditioner, Misakian says readers must investigate the details of these options for themselves.

You can download the paper here:

http://www.nist.gov/cgi-bin//get_pdf.cgi?pub_id=903669

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