Recent heat wave-related blackouts in California and New York are at least partly being blamed on creaky transformers, circuit breakers and cables.
And smaller outages in cities such as Detroit, Chicago and Houston will be investigated to see if aging parts played a role, says Stan Johnson of the North American Electric Reliability Council.
Low investment in interstate transmission lines could lead to more regional blackouts, such as the one that hit the Northeast in August 2003. The trends show the need to pump more money into the power grid to meet demand, federal officials say. That would mean higher consumer rates.
"There is a need to spend more," says Gerry Cauley, vice president of standards for the reliability council.
While Johnson says the USA's power grid handled the heat spell well, key trouble spots were exposed:
• In Queens, N.Y., as households boosted their electricity usage during last week's heat wave, high-voltage feeder cables failed, plunging 25,000 Con Edison customers into darkness for up to nine days. Reports to state regulators show that the Queens system had 71 equipment failures last year and that many parts were 30 to 60 years old.
"Age is not necessarily an indicator of performance," Con Ed's Chris Olert says.
While even new cables break if stressed, older ones have more cracks that absorb corrosive moisture, says Gerald Wilson, a power-system expert at Massachusetts Institute of Technology. New York last year told Con Ed to spend $3.4 billion on upgrades by 2009.
• In Southern California, more than 1 million customers of Southern California Edison and the Los Angeles Department of Water and Power have lost power since July 13. Utility executives blamed the record heat wave and transformers that weren't built to handle customers' new central air conditioning systems, multiple computers and big-screen TVs.
Southern California Edison already planned to spend $7 billion by 2011 on upgrades, and may seek further rate increases for extra transformers, Senior Vice President Ron Litzinger says.
• In Franklin, Tenn., 10,000 homes lost power for 90 minutes in May as a 40-year-old surge protector broke.
A bigger weak spot may be the transmission lines that bring electricity to regions. As demand and power supply rose 2.5% a year from 1993 to 2004, delivery lines grew just 0.75%, says the Federal Energy Regulatory Commission.
"You're raising the prospects we will see another major regional blackout," FERC Chairman Joseph Kelliher says.
New rules allowing utilities higher returns should spur construction. Yet, local regulators may be loath to clear rate increases for other upgrades with rates in some states soaring, Johnson says.