You'll presumably pay a lot more in power utility bills if you're charged for so-called “reactive power” as an industrial customer who uses banks of “uncompensated” motor loads facing the AC mains. But as so many articles over the years have pointed out, the typical residential consumer won't save much by swamping out all that inductance at his house. That's because his “power” meter keeps track of the total energy actually consumed, not reactive power or apparent power. Beyond that, various environmental and medical concerns over such issues as greenhouse gas emissions from the power plant are beginning to creep into the consumer's head, even those who aren't particularly sold on global warming.
Up to now, power-factor-correction (PFC) has been largely about how much money Joe Average saves each month. But in practice, the critical economics derives from the utility's perspective. So what's the direct savings to the utility, whose rates determine — albeit in an unknown, indirect way — what residential customers pay for energy per kilowatt-hour? And what would be the plant's overall transmission efficiency if PFC were applied universally?
The utility might save about a penny a day per household appliance, as suggested in National Institute of Standards & Technology (NIST) Technical Note 1654 by Martin Misakian, et al. But even that number is rather buried in the article's last sentence, and we're still awaiting answers to what the integrated savings might be for a utility serving tens or hundreds of thousands of customers, each of whom uses appliances that present something other than a resistive load to the utility's power source.
Oddly enough, representative numbers are hard to come by and maybe don't even exist. None of the majors in the big-energy business — from state utility commissions to the Department of Energy (DoE) to Electric Power Research Institute (EPRI) to NIST — have yet offered me a methodology to answer the big question. Perhaps the lack of a ready response owes partially to the perceived sensitivities of manufacturers in the business of providing power-factor-corrected equipment and the various marketing over the years focused on increased efficiency and cost-savings. On the other hand, is an accurate analysis truly doable?
“The study would be worthy of a Ph.D. thesis,” says William Rynone, whose 2007 article “Is Power Factor Correction Justified in the Home?” (Power Electronics Technology) did some number crunching to conclude the resident doesn't gain directly from PFC. “I don't know if it's possible to do,” he said, underscoring the complexity of even defining an “average” household. “I believe you would need teams of mathematicians, engineers, and systems/maintenance personnel to figure it all out.”
Rynone's article, from the resident's perspective, looked at several motor-driven appliances based on a 1-HP motor, which included a refrigerator, washing machine, air conditioner, and well pump. He calculated the residential system losses — basically the power losses in a given two-conductor, 25-foot section of #12 copper wire leading from the main panel to the various appliances with unity power factor. Then he determined the difference in power loss for the appliances with a lagging PF of 0.75 (current flow increases), suitably scaled over time of use per day and over a month.
The difference to the resident was 8 to 14 cents a month for the major appliances (this did not include the air conditioner) for a typical electric bill of $60 to $80 (at 10 cents per kW-h, includes use of unity PF devices such as lighting, toasters, electric stoves). That represents a savings of about 0.2 percent in the total monthly bill.
Misakian's group, looking at the issue from the utility's standpoint, similarly calculated how much energy would be saved because of lower resistive losses in a distribution system corrected by placing suitable capacitance (108μF) across a central air conditioner. Assuming a distribution system that looks back at the utility and sees a system resistance of 0.05Ω, Misakian's group calculated the utility would consume 4.4W less as the result of a reduction in I2 R losses. The resulting energy savings for powering the air conditioner, which they assumed would run for 12 hours a day over a little less than half the year, was thus 52.8W-h/day. At 20 cents per kW-h, their calculated cost savings for the utility would be about $1.80 for that approximate half-year period. The issue of using active or passive PFC didn't come into the discussion in either Rynone's or Misakian's article.
But given the new focal point on PFC and the various new ways customers can save on energy — even sell it to the power utility –would a working power-delivery characterization now be that important? Curiously enough, PFC marketers' initial “low-profile” argument for PFC — cutting down on greenhouse-gas emissions from the power plant — has seemingly become its ace-in-the-hole. Beyond our breathing cleaner air, it's to some degree about global warming, which is becoming more serious an issue than paying a relatively small bill in a fiat-based monetary system. Global temperatures have certainly been higher since the earth formed, but today's rate of change in the modern world looks unprecedented.
I've been unsure about much of the science in those studies, and a number of skeptics make some noteworthy criticisms. On the other hand, I now hand it to you by way of a null hypothesis: Keeping in mind a 2°F increase in 100 years is considered rare at this point in our evolution, discuss the last time the average (smoothed) yearly temperature increased 2°F over just a 20-year span in a virtually untouched environment — for example, as measured at my rural locale and in line with similar sites around the country. Then, assuming you agree that global temperatures have gone up, tell me the naturally-occurring causes you believe are responsible for such an increase — reportedly greater for the US than around the rest of the world.