Montville — As sunlight spills through the doors from the senior courtyard at Montville High School, the ceiling lights dim. With students still in class awaiting the day's first charge to the cafeteria, the other end of the hall remains empty and darkened.

Then, with a buzz, a tide of teenagers courses through the corridors, and one by one the ceiling LED lights — 1,600 networked, motion sensor-equipped fixtures that automatically dim or come to life based on activity or natural light — brighten the path to pizza.

"In night mode, it's only every third light in the hallway and they're only on for two minutes," said Facilities Director Steve Carroll, who's partnered with Eversource Energy to spearhead a host of energy efficiency overhauls at the high school, including a lighting system seen in a few city halls, business offices and manufacturing plants, but no other schools in Connecticut.

The efficiency moves — including high-tech ventilation systems that monitor carbon dioxide and control rooftop HVAC unit dampers to meet fresh air needs, and low-tech adjustments of window blinds to "harvest" daylight — have helped the school shave electricity demand in half. The building previously consumed about 1.3 million kilowatts per hour every year — now it's closer to 600,000 kilowatts per hour annually.

The school consistently requires less than 200 kilowatts per hour monthly, whereas many months in 2017 saw demand approach or exceed 300 kilowatts per hour.

Carroll said 200 kilowatts per hour was a "crazy" low amount of energy consumption for a 176,000-square foot building. Carroll and Eversource Engineer Bryan Parsons said the school now uses an electric meter that's nearly the "smallest commercial-size meter," something that typically would be seen at a gas station, not a sprawling educational facility built five decades ago.

A few years ago the building would remain awash with light from energy-churning fixtures until almost 10 p.m. every night. But Carroll says, "Doing efficiency is finding how you make a building efficient for its point of use."

"The school is open 17 hours a day, but it's only truly an educational facility for seven to eight hours," he said in the school last Friday. "When there's no kids in the building, what are we? The building doesn't demand the same codes and light levels," so now the school darkens much earlier.

The two-year, $400,000 smart lighting project — for which the school received an Eversource grant — relies on a control system designed by Georgia-based Acuity Controls. The system paid for itself in just over a year, Carroll said.

Similarly, the school spent $1,000 to add hot water controls into its building management system, shutting off hot water on nights and weekends — cutting annual heat and hot water costs by half, from $24,000 to $12,000.

"Every penny we save on utilities is a penny we can use to hire a teacher or paraprofessional or something else for the students," Board of Education Chairman Bob Mitchell said. "Steve is rightfully proud of everything he's done."

Improved natural gas boilers are outfitted with outdoor air reset controls that lower boiler water temperatures when it's warmer outside, and ramp up the temperatures when it's colder outside. Radiant heaters warm up the air already in the building before outdoor air is introduced once the building is occupied.

Many buildings have switched to natural gas boilers but haven't changed the way they operated when they were using oil, Carroll said. By heating the building over a slower, longer period of time than when it used oil, the school has saved at least $19,000 annually in demand charges. Eversource account executive Andrew Brydges noted the boilers in Montville could switch back to oil if need be.

"We've been able to identify and share with schools not only things they can invest in that have a payback, but also no-cost measures," like optimizing energy management systems, Brydges said. "Not everything requires a cost up front."

In Susan Laurencot's English class — an efficiency test lab of sorts, with a 78-watt Smartboard compared to the previous 420-watt version — the goal is to consume no more than 1 kilowatt hour per day.

"It's an issue that's very important to me," said Laurencot, who drives a Chevy Volt and previously owned a vehicle that ran on vegetable oil. "My students work on critical issues, so it's something that is really prevalent in my teaching — what are the problems in the world today and what are some of the steps we can take to alleviate them?"

The students last year picked a light blue color to paint the room for optimal reflection of natural light, helping the ceiling LEDs conserve energy. Laurencot also instructs students to keep charging electronics to a minimum.

Using software from Middletown-based Artis Energy Solutions, Carroll's team can pull daily, monthly and annual reports on almost every facet of energy demand and consumption in the building.

In the main office, Carroll listened to the hum of the air conditioners — the school saves energy by being just 21 percent air conditioned — and hunched over a computer screen to watch the temperature cool to the right level. He correctly predicted when the air conditioning would shut off, which he argued improved not only efficiency but the quality of the workplace, now a quieter space.

"We're kicking butt," he said. "It's a really cool building. It's not a beautiful building but we've taken it from the 1960s and made it a building of the future, energy-wise."

Officials say the school will be powered by 90 percent renewable energy by 2020. The school district may save about $2 million over 20 years on electricity costs after Con Edison installs a solar field on 2 acres near the high school and Leonard J. Tyl Middle School, where a smart lighting project is also in the works. When the solar project is complete, electricity will cost about 10 cents per kilowatt hour, Carroll estimates, compared to about 17 cents per kilowatt hour today.

b.kail@theday.com