Thousands of metro area Xcel Energy customers were unable to control their home thermostats earlier this week when temperatures climbed into the 90s.

Voluntary participants in the company’s AC Rewards program allow Xcel to control their “smart” home thermostats during hot summer days when demand for electricity and air conditioning is at a peak.

Typically, program participants “have the ability to opt out of control events at any time,” according to an Xcel description on its website.

On Tuesday, as temperatures rose into the lower 90s in the metro area, Xcel took complete control and locked thermostats because of an “emergency situation.”

“This was a very unique circumstance where we had to call this,” said Emmett Romine, vice president of customer solutions and innovation with Xcel.

More than 22,000 Xcel AC Rewards customers were locked out of their smart thermostats for hours on Tuesday, according to Denver7. On social media, dozens of Xcel customers complained about the experience, with some reporting home temperatures as high as 88 degrees.

Impacted thermostats on Tuesday were locked in a “plus four-degree offset,” Romine said. So, if a customer had the thermostat set turn on air conditioning at 78 degrees, it locked at 82 degrees.

Customers who participate in the program are paid a one-time $100 enrollment credit to join, along with $25 for annual participation, according to Xcel. The program is billed as a way for customers to help Xcel better manage peak demand hours and ease the strain on the electrical grid.

Tuesday’s “emergency” was the first time in the six-year program’s history that area participants were locked out, Romine said. The emergency stemmed from an unexpected energy outage in Pueblo combined with local hot weather and heavy air conditioning use.

“This is not something we see ourselves triggering very often in the future,” Romine said. “This is a scenario we don’t want to use.”