CEDAR RAPIDS — Alliant Energy customers might do a double take when they check their latest energy bill.

But Alliant officials say that while recent bills are unusually high, they are accurate — caused by an uncharacteristically hot summer.

Justin Foss, Alliant spokesman, said the recent weather has not just been warmer than usual, but it’s been consistently warm — which has air conditioners running more than normal.

“When the heat sticks around day after day, it’s a compounding effect, so you use more and more energy,” Foss said.

Alliant uses a computer system to check customers’ monthly usage to catch possible mistakes in the meter-reading process, Foss said. When the system finds usage that is much higher or lower than normal, the bill is sent to a representative to review the bill and have the customer notified.

The process occurs hundreds of times a day, according to an Alliant statement to customers.

However, Foss said a newer system has different parameters for catching high or low bills.

“The new system we have has much tighter tolerances on that and we were unprepared for the amount of heat and how it would impact the number of bills that needed to be manually reviewed,” he said. “We were not able to manually review all these bills.”

Foss said the bills came as an understandable surprise to many customers — who would have typically been notified in advance by Alliant.

Foss said he didn’t have a number on how many customers were effected, but said the issue reached a wide variety of customers.

Jason Arends, who lives in Cedar Rapids, is one of those customers. He said his bill, which typically comes in at about $150 a month, was more than twice that.

“It just sucks as a customer because you’re stuck with them. You have no alternative — personally I’m kind of sick of them,” Arends said.

Meanwhile, Don Tormey, spokesman with the Iowa Utilities Board (IUB), said the board was aware of Alliant’s statement to customers regarding rates and has received written complaints from more than 80 Alliant customers.

“Over the weekend, the IUB’s customer-service section started receiving email correspondence from customers and that has continued today (Monday), along with several phone calls,” he said in an email Monday.

Tormey said customer-service staff are investigating the complaints and will determine a resolution pursuant to the board’s procedure rules.

According to Alliant’s statement to customers, utility officials are adjusting their methods to prevent multi-month estimations during times of extremely hot or cold temperatures. Meanwhile, the utility company temporarily has stopped the disconnection process for customers affected and are waiving late-payment fees for affected customers.

Alliant Energy also announced plans to hire more employees for the review process.

Alliant customers with questions or concerns are encouraged to call 1-800-ALLIANT (800-255-4268).