The Hidden Costs of CFLs

The Hidden Costs of CFLs

Will there be a price to pay for the increased residential use of electronic ballasts with low power factor ratings?

Mandates in the Energy Independence and Security Act of 2007 call for lamps that use 25% to 30% less energy by 2014 and 70% less energy by 2020 — ostensibly putting the incandescent bulb out to pasture. With light-emitting diode (LED) technology still out of reach for the average consumer, this essentially paves the way for compact fluorescent lamp (CFL) products.

Already, many electric utilities have launched rebate programs offering free or low-cost CFLs to their customers. In addition, high-profile campaigns and higher energy costs have piqued consumer interest in energy efficiency and green products for their homes, resulting in increased sales of CFLs from big-box stores. The majority of bulbs being used to replace incandescent lamps are electronically ballasted, screw-base CFLs. Although some of the programs offering these types of bulbs require purchase of power factor-corrected bulbs to be eligible for rebates and other incentives, many do not.

CFLs can replace incandescent lamps roughly three to four times their wattage, saving up to 75% of the initial lighting energy, according to the U.S. Department of Energy (DOE). Yet, incandescent lamps use power as it is supplied by the electric utility, whereas electronically ballasted, screw-base CFLs must contain circuitry that corrects for poor power factor and total harmonic distortion (THD) ratings. When uncorrected, CFLs draw currents in bursts, altering the electricity that flows through them and increasing line losses on the electric utility network, which can cause transformers and cables to burn out more quickly. This has led to several recent studies that claim any efficiency gained through the use of electronically ballasted, screw-base CFLs with low power factor ratings and high THD percentages is lost in the transportation of power that runs through them. Some argue that electric utilities may begin charging residential customers fees to compensate for expensive corrective measures required to combat the problem and the additional generation resources required.

Uncorrected electronically ballasted, screw-base CFLs are not the only cause of non-linear loads from electrical devices in residential applications. Over the last two decades, the shift from simple mechanical devices to more sophisticated home electronics — such as audio and video equipment, personal computers, and microwaves/kitchen appliances — is also responsible for increases in THD to the voltage waveform that electric utilities supply to their residential customers. However, the recent meteoric rise in the popularity of this type of CFL has some industry experts warning against bulb-for-bulb replacement of incandescent lamps, even in the face of proven wattage savings.

Power factor is the ratio of the real power flowing to the load to the apparent power. Power factor ratings range from 0 to 1, with 1 indicating a perfect power factor. When a load draws current that is not “in phase” with the voltage waveform, or draws a current that differs from the sinusoidal waveform provided by the electric utility, the power factor is less than 1. Poor power factor causes inefficiency in the delivery of electricity to the end-user, requiring more energy to compensate for losses on the line. For example, a load with a power factor of 0.5 will require twice as much current as a load with a power factor of 1 for the same amount of usable power.

Standards set by the American National Standards Institute (ANSI), Washington, D.C., and the National Electrical Manufacturers Association (NEMA), Rosslyn, Va., recommend a power factor of 0.9 or greater for electronic ballasts. Yet, Energy Star, the joint program of the U.S. Department of Energy (DOE) and the U.S. Environmental Protection Agency (EPA), requires a minimum power factor rating of 0.5 for screw-base, electronically ballasted CFLs. “In our testing for Energy Star, we haven't found any CFLs less than 0.5, but they're not 1, either,” says Peter Morante, director of energy programs for Rensselaer Polytechnic Institute's Lighting Research Center (LRC), Troy, N.Y.

For a variety of reasons, U.S. manufacturers have not produced many power factor-corrected CFLs. A lower power factor allows them to keep the cost of the bulbs down, which greatly helps market penetration. “The original thought was to let the power factor go a little bit lower to reduce the first costs of the lamps,” Morante explains. “For a rating above 0.5, you have to add something to the electronics, so that will up the cost of the lamp.”

Size is another factor in setting the power factor rating standard. “Any device that uses some sort of power supply or power filter is going to put some harmonic distortion into the load, because the only way to make it yummy and clean is to make it huge and expensive,” says Alex Boesenberg, technical manager for the Lighting Systems Division of NEMA. “There are people that make high power factor CFLs — I think all my manufacturers have a design handy if they need it — but the cost and the footprint of those things have made them undesirable.”

Even so, CFLs can cost three to 10 times more than comparable incandescent bulbs. In general, the higher the power factor, the higher the cost of the lamp. Under this rule, you get what you pay for, says Doreen LeMay Madden, founder and principal designer for Lux Lighting Design, Belmont, Mass., and chairman of the Residence Lighting Design & Application for the Illuminating Engineering Society of North America (IESNA), New York. At a power factor rating of 0.5, a 15W screw-in CFL will actually use 30VA of energy and, in some cases, the consumer may not be receiving the same light output the incandescent provided. However, the consumer may be unaware of this exchange rate.

Power quality has traditionally been thought of strictly as an issue for the electric utility. The electric meters on residences measure watts, so consumers realize the wattage savings indicated on the lamp's packaging through savings in their energy bill. “They'll see that 75% savings,” Morante says. “The meter on the house doesn't measure power factor.”

Unlike commercial customers, residential energy users currently aren't charged extra to compensate for loads with low power factors. “The end-users don't fully realize that these low power factor compact fluorescents are not using the small amount of energy that they think,” LeMay Madden says. “They're using twice the amount of energy, plus they're causing distortion in the sine wave. The lower the power factor, the more distortion you get.”

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