Just what is Power Factor you ask?
Power factor is like a percentage score of how well a motor or a transformer uses the power that it draws through your electric meter. A power factor of 100 is as good as it gets. Lower power factors cost you money. Think of it as a percentage 100% is great and 75% leaves a lot of room for improvement.
It is the nature of alternating current that things like electric motors cause an active and a reactive current flow. You get charged for both but the motor only uses the active portion of the total current. A high reactive current flow causes a low power factor.
What you need to know
Not all electric appliances have a low power factor. Appliances that have heating elements have a 100% power factor. That means that your electric water heater, stove, oven, electric blanket and toaster are not the problem. Old fashion incandescent light bulbs also have a 100% power factor.
Motors and fluorescent lights have lower power factors. Our homes have motors for air conditioners, furnace fans, refrigerators, chest freezers, clothes washer and dryers, dishwashers, sump pumps, garage door openers, power tools, fans and more.
Older motors and inexpensive new motors have power factors of about 75% or so. Newer high efficiency premium quality motors have power factors of around 86%.
This means that for devices that have an average power factor of around 75% you are paying for 25% more for power than you could be.
How is the problem fixed?
Businesses that use large amounts of electricity use power factor correction capacitors to save money. This is a proven, well-established, method to correct a low power factor. The process of having an electrical engineer analyze electric loads and select the correct size equipment to install requires a big investment.
The cost of engineering and hardware is a good investment for a business because it reduces their electric bill two ways. It reduces the amount of power that they are billed for plus it avoids penalty charges for low power factor. Most utility companies hit their largest customers with an extra charge for power factors of less than 90%. The exact numbers very for each power company and by State regulations.
What can you do at home to save Money?
Until recently, it was not worth the cost to install power factor correction equipment in homes. Two things have changed that.
- The increased cost of electricity
- The availability of low cost simple to install equipment
Low power factor can be corrected by adding a simple device at the main electrical power panel in your home. Power factor correction capacitors can save 10 to 25% of your home electric bill by reducing the amount of power that passes through your electric meter. The exact amount of your savings will depend on how much of your power bill is from motors and fluorescent lights.
You can expect to invest about $315 for equipment plus the cost of installation. Installation is a 30-minute job that may take electrical contractor an hour to do. The work involves mounting a small gray box beside the main electrical panel, adding a 20-amp circuit breaker in the main panel and wiring the box to the panel.
If your monthly home electric bill is always more than $100, installing a power factor correction capacitor is likely to be a good investment for you. If your monthly electric bill is more than $200, payback is likely to be a year or less. The higher your electric bill the faster the pay back and higher the return on your investment.
Folks with high air conditioning or electric heat pump costs will get the best return on investment with power factor correction.
Warning this is not for every one.
Homes that have monthly electric bills lower than $100 will actually loose money by installing power factor correction equipment. That is because the added equipment uses a small amount of power all the time. It only saves money for folks that have above average electric bills.
For big power users adding power factor correction is the next layer of electrical energy savings after you have updated to Energy Star appliances and switched to fluorescent lighting.
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