Kristen Budd pumps her legs, her ponytail bobbing, as she works out on an elliptical machine at the University of North Texas recreation center.

It’s similar to other workouts the UNT junior has had before — but today there’s a difference. Every time Budd moves her legs, her kinetic energy is harnessed by the machine, sent to a metal box on a wall nearby and converted into usable electricity that could supply wattage to the building’s television monitors or light bulbs.

UNT will officially become one of the largest human power plants in the country, as the last of the 36 elliptical machines at the university’s recreation center are outfitted next week with a device capturing kinetic energy, officials said.

A typical 30-minute elliptical workout could produce enough electricity to power a light bulb for 2 1/2 hours or a laptop for an hour, said Laurie Klein, senior associate director for the recreation center.

DRC/David Minton

The ReRev system hooked up to these elliptical machines, shown Thursday at the Pohl Recreation Center at the University of North Texas, collects the users’ kinetic energy to generate electricity.

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“UNT has made a huge commitment to sustainability and this is part of that, to educate students to be part of that,” Klein said. “It’s an excellent workout, and it helps the environment.”

UNT is the second Texas university to have the devices installed on machines owned by the university. UNT paid $19,450 to Florida-based ReRev for the devices and installation.

Texas State University in San Marcos had 30 similar exercise machines installed with the devices in December.

There are roughly 25 other universities in the United States using the device.

Along with capturing the kinetic energy of elliptical machine users, the device absorbs the heat displaced from the machines and will help the recreation center use less energy to cool the building, said Greg Johansen, vice president of sales for ReRev.

“If you work out for half an hour, the internal components can get to 285 degrees. It’s like running a bunch of hair dryers,” Johansen said. “This [the device] insulates the heat in there and is another way to save on energy.”

While UNT may never recoup the money spent on the devices, the decision to outfit existing elliptical machines fulfilled the university’s larger goal of sustainability and student education, Klein said.

“We hope to see a cost savings, but there’s a student demand for universities to go green and this is part of that movement,” she said.

Elliptical users are able to see the fruits of their labor by viewing a computer monitor near the machines that calculates the total kilowatts being produced.

DRC/David Minton

The University of North Texas has installed ReRev’s kinetic energy-capturing devices on elliptical machines at the Pohl Recreation Center. The devices send captured energy to a nearby box, shown Thursday in Denton.

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Though Budd, a self-proclaimed “tree hugger,” said she feels better working out on an elliptical machine that helps the environment, the low resistance level she set on the machine means she doesn’t put out as much kinetic energy. Power generation increases with the machine’s resistance level, Klein said.

The resistance levels range from a low of one to a high of 20.

Justin Piller, a personal trainer at the UNT recreation center, said unless the machines’ users are training for a marathon or a competition, they rarely touch a level 20 resistance.

Instead, most of Piller’s clients stay around a level 10 or 15, which is still challenging, he said.

UNT student Sara Rose, another elliptical user, said helping produce electricity for the recreation center is a nice bonus on top of her workout.

“It’s good; I’m able to work out and help the university,” she said.

CANDACE CARLISLE can be reached at 940-566-6889. Her e-mail address is ccarlisle@dentonrc.com.