The temperature inside Carmen Bruce and Lauren Taketa’s fifth-grade classroom in Waipahu would sometimes reach a stifling 100 degrees in the late summer months. The co-teachers say oscillating floor fans provided little relief, making it a challenge for students to concentrate throughout the day.

This school year the classroom has been outfitted with an air-conditioning system and ceiling fans that keep the room cooled to the mid-70s. It’s one of more than two dozen classrooms at Honowai Elementary to receive air conditioning this year following a campus-wide campaign to reduce energy use. The state Department of Education says the campus received “the most extensive deployment of energy and sustainability efforts.”

“It was hot, like really hot, especially after recess,” sixth-grader Jason Gill, 11, recalled. “Now we have more concentration about our work and I feel comfortable.”

“Last year,” added fifth-grader Jheanna Carlos, 10, “I didn’t have AC, and that kind of took away our learning time, because everybody had to go in front of the fans to cool off and that look like 10 minutes.”

Bruce and Taketa have seen a big difference as well.

“I think they focus better, they’re willing to work harder, they’re just happier, they’re more comfortable,” Bruce said. “It makes it easier to teach, too.”

Last fall, when the Department of Education began deploying portable air conditioners as an emergency response to record-high temperatures, Honowai Elementary’s electrical system couldn’t handle the increased load.

“When we started plugging them in, we were tripping circuit breakers left and right,” Dann Carlson, assistant superintendent for school facilities and support services, said Thursday during a tour of the school. “So we knew that this was a school that was at its electrical infrastructure capacity, and we couldn’t have AC.”

As part of the Department of Education’s sustainability program known as Ka Hei, the DOE challenged its energy contractor, OpTerra, to find energy efficiencies to reduce the school’s electrical use.

“The good thing is it’s been very successful and we have been able to provide new AC for 27 classrooms here” just by improving efficiencies, Carlson said.

Overall, energy usage was reduced by 25 percent from the previous year through changes including replacing all interior and exterior lighting with LED lights, replacing inefficient motors in the cafeteria’s refrigerator and freezers and adding efficient air ventilation to the cafeteria’s kitchen.

Brandon Hayashi, regional manager for OpTerra, said the LED lighting changes alone reduced the school’s daytime lighting usage by 42 percent, and its nighttime usage by 62 percent.

The DOE invested $1.2 million, an average of $50,000 per classroom, on the Honowai project, which it hopes will serve as a model for other schools.

To further offset the school’s energy use, OpTerra installed 100 kilowatts of photovoltaic panels — the maximum output capacity allowed per meter by Hawaiian Electric Company.

Officials said the campus consumed 463,000 kilowatt-hours last school year. The efficiency measures reduced electrical use by 115,000 kilowatt-hours and the photovoltaic system will generate 200,000 kilowatt-hours annually.

“I think what it proves is that efficiencies is truly a resource that needs to be maximized,” Hayashi said. “If we can get people to understand that, then we can have more and more schools that are maximizing efficiencies, thereby allowing for not just a reduction in energy, but a potential rampway for air conditioning.”

The Ka Hei sustainability program was launched two years ago with the ultimate goal of having public schools generate their own energy. The 100-kilowatt cap imposed by the electric utility on photovoltatic systems has somewhat hampered that effort. Still, OpTerra and the DOE have secured 81 agreements with HECO to install photovoltaic systems at 74 schools (some schools have more than one meter) by the end of the year.

That will bring the total number of schools with solar-powered PV systems to 114 out of 256 schools statewide.