No, peak, no shortage -- so what's the deal with power alerts?

As a major heat Midwest wave hit a crescendo Friday, Iowa's major utilities weren't expecting new electric demand peaks or power shortages.

Consumers might have thought so, however, by the way utilities were acting. MidAmerican Energy and Alliant Energy were remotely powering off air conditioners at thousands of Iowa households and curtailing power supplies at large customers with interruptible service.

The measures reflect the way the utility industry and regulators have standardized proactive measures to keep strain off the electric grid and keep electric prices from skyrocketing due to sharp demand peaks.

"We haven't seen as much demand (during this heat wave) as we have in the past," said Justin Foss, a spokesman for Alliant's Interstate Power & Light Utility in Cedar Rapids. Foss said his best guess is that the economy has kept demand below peak levels.

Alliant Energy was getting close to its last peak electric demand, wich was 3,699 megawatts on July 18, 2011.

MidAmerican's last peak demand came on July 19, 2011, when customers used 4,752 megawatts. Unofficial loads this week were slightly over 4,000 megawatts, MidAmerican spokeswoman Tina Potthoff said.

Linn County Rural Electric Coop had curtailed power to about seven customers who are on voluntary interruptible accounts, Membership Services Coordinator Steve Carroll said. He said the distribution cooperative has no problems getting enough power, however.

Controlling peak demand during hot conditions still pays big dividends, however, for both consumers and utilities.

The more peak electricity consumers buy, the more utilities must turn for power to their less efficient generating units that ordinarily sit idle, and the more they must buy power from wholesale power markets at high prices that reflect the relatively thin margin of supply over demand during summer months, Foss said.

More expensive power purchases would be reflected in consumers' electric bills in the coming months, Foss said, through the fuel cost riders on the bills.

The higher demand peaks are also factored in when the Iowa Utilities Board determines the electric reserve margins that utilities must have built into their generation systems, potentially affecting rates.

Caroll, of Linn Coop, said the voluntary conservation programs help relieve congestion on the overall Midwest power grid, which is managed by the Carmel, Ind.-based MISO.

"It's just prudent," Caroll said. "There is also a cost factor to it, as you bring on more power plants."

Customers already pay considerably more for electricity during the summer months because of summer/winter rate differentials in the rate structures of utilities. The higher rates kicked in June 1. For Alliant customers, they can increase the cost per kilowatt hour of electricity from 19.3 percent to 172.5 percent. For MidAmerican customers, the range is from about 14 percent to 107 percent.

Alliant also Friday issued a "Peak Alert," which encourages ordinary customers to conserve electricity. Foss said the Peak Alerts are issued in response to Iowa Utilities Board regulations that are based on a temperature formula.

When temperatures exceed 95 degrees Fahrenheit for one day and are expected to rise above 95 degrees the next day, the utility calls a Peak Alert for the second day. A peak alert will also be issued for the third day if temperatures are expected to be above 90 degrees after two straight days of temperatures over 95 degrees.