It's simple to go online and compare the on-time rates of airlines, the quality of coffee makers or the graduation rates of high schools.
But it's not so easy for Duke Energy or Progress Energy customers in North Carolina and South Carolina to find out how well the utilities perform their most basic task: delivering electricity.
Utilities closely monitor power-outage data, which helps them spot problem areas and decide how to spend maintenance money. They regularly compare their performance to peers, using simple reliability indexes.
Duke and Progress, which plan to merge by year's end, also share their performance data with North Carolina utility consumer advocates - in reports marked "proprietary." The information can't be released to the public, although 36 other states require similar information to be reported and made available.
Robert Gruber, executive director of the N.C. Utilities Commission's Public Staff, which represents utility customers, said the Public Staff was "re-evaluating whether that should be treated as proprietary."
Even if Duke and Progress publish their numbers, their reliability indexes alone are of limited use. Without regional or national benchmarks, which aren't available to the public without some digging, the utilities can't be compared with those in other states.
The most widely used index of how often the lights go out measures outages of five minutes or more. Utility customers, however, say frequent, momentary blips that require resetting of digital clocks throughout a household can be just as irritating.
Asked for information, Duke first pointed to reliability indexes buried in 223 pages of staff testimony about the North Carolina rate increase it filed for last month. The company later supplied more figures.
The indexes show that Duke has steadily improved since 2003 in the frequency and duration of outages in North Carolina and South Carolina. Progress Energy's numbers, supplied at The News & Observer's request, show improved performance after 2006, followed by an uptick of outages in 2010.
Utilities commonly delete from the indexes major events out of their control, such as ice storms or hurricanes. That gives a better indication of their day-to-day performance.
Storms are dominant factors in reliability, especially this year.
Mike Hughes, a Progress Energy spokesman, said the utility has experienced an 8 percent increase in lightning strikes this year throughout its service area compared with the past five years. In its northern region, which includes the Triangle, strikes were up 14 percent.
Some of this year's outages were planned, Hughes said. He added that 18 percent of the outage times were for system maintenance and smart grid updates.
Duke Energy also has seen an increase.
"The first six months have probably been one of the toughest storm years we have ever had," said Jim Stanley, Duke's senior vice president for power delivery. "There were stretches for two months when we had folks working multiple nights, week after week, and of course they get tired. Customers don't care how tired you get, they want the lights on."
Rebecca Horton, who lives in an older Charlotte neighborhood, Madison Park, has lost power five times after storms since early April - the first outage lasted three days. A camping headlamp and battery-powered fan have become essential survival tools.
"There has to be something systemically wrong, but we don't know what," Horton said. "I just wonder if we're unusually high or, statistically, it's just sort of our turn."
The known rankings
Stanley said several factors make some spots more outage-prone than others. Among them are the length of the electric circuit that serves an area and the risk it faces from falling tree limbs, car crashes and other perils.
The state's Public Staff sometimes uses reliability data to investigate customer complaints. The N.C. Utilities Commission has cited the information in ruling on rates. It commissioned a full report on the utilities' response to outages from a 2002 ice storm.
Utilities and regulators say customers rarely ask about reliability.
"We don't get a lot of complaints about outages," said George Sessoms, deputy director of the commission's electric division. "I hope that reliability is so high that consumers are not concerned about that" as Duke and Progress prepare to merge.
Hughes, the Progress spokesman, said his company doesn't make the reliability indexes available to customers because they can be hard to understand.
"We have not felt like there's a reason to do that because the context has to be added, and the context is somewhat voluminous," he said. Progress instead uses customer surveys to help identify performance problems and, like other utilities, is making increased use of its website and social media to share outage information.
Progress Carolinas jumped to third best in the South in this year's J.D. Power and Associates annual survey of residential utility customers. It ranked fourth last year. Duke Carolinas fell to sixth this year from first in 2010.
Thirty-seven states make reliability information publicly available, according to a 2008 study by the Lawrence Berkeley National Laboratory in California. The study erroneously listed North Carolina among them.
The problem remains of how to compare one state's utilities with others regionally or nationwide. Only now are utilities and their regulators moving toward a standardized way to use their data, said Joe Eto, a staff scientist who works on reliability issues at the Lawrence Berkeley lab.
"The issue of comparing one utility to another is a very complicated matter," Eto said. "There are different definitions and differences among utilities. Some utilities are in the desert with no trees."
Alice Bumgardner, who lives in the often-dark Madison Park neighborhood, cares only that "every time it storms, our power goes out. This is not an exaggeration.
"We had sporadic outages prior to this but it usually took a very violent storm to cause it," she said by email. "Now I feel like every time it just rains hard, I have to brace myself for darkness."
Said Stanley, the Duke executive: "Usually there's a good reason for that. But sometimes there's not."
News & Observer staff writer John Murawski contributed to this report.