Pennies turned to dollars, dollars turned to thousands of dollars when determined students did an energy audit of their public school in Louisville.

The eighth-graders in Brian Slobe's Earth sciences classes at Monarch K-8 School in Louisville this month found that some $4,000 in electricity can be saved in one year.

Doesn't sound like much?

Well, they extrapolate that some $250,000 could be saved in their school district, Boulder Valley, which means the savings statewide could reach into the millions.

That's just in electricity. Heating inefficiencies from ancient boilers and bad insulation in Colorado's public schools is assumed to run into the tens of millions of dollars each year.

"It was extremely fun," eighth-grader Harnek Gulati said on Thursday. "It was so much better than learning out of a book."

Their tools were Xcel energy bills, tables on kilowatt usage, meters that measure the watts when an appliance is on, off, and almost off.

Their modus operandi was to form teams of three and then audit classrooms, cafeteria, hallways, the gym, the front office.

Too many lights are left on at night, they said. A few are needed for security, but why leave on all 32 lights in each classroom?

Thursday, Reese LeBlanc ticked off the bad news garnered from one teacher's classroom:

"She has three lamps and three clocks. They leave the computers on 24 hours a day. If she left them on nine hours a day, she'd save $54.93.

"If they didn't use the TV as a clock, the cost would be 70 cents a year instead of $34."

Together, total easy-to-achieve savings amount to $248, he said.

His team has charts, statistics, everything to back it up.

Some ideas aren't practical.

The overhead projectors take a lot of energy, but the alternative — handouts to all the students — has an energy cost, too, they learned.

And the suggestion to get rid of the classroom's electric pencil sharpener would save a whopping 61 cents a year.

But the teams that audited the hallways quickly discovered that while the school was built with big windows to use natural light, there are two fluorescent bulbs in each fixture.

Why not just one?

They tried it, found out that the lighting was still fine, and calculated that it could save several hundred dollars a year.

Principal Rich Glaab is behind the one-bulb per fixture idea and behind Slobe's latest venture: to apply for a solar energy grant and put solar collectors on the school's roof.

"The things we plug in, the electricity we use in schools, we've just looked at them over the years as a necessary evil, part of the cost of doing business, that we have no control over," Glaab said. "Brian and his students have shown that we do have some control over it. The savings are phenomenal."

Slobe has been doing energy audits with his eighth graders for five years now, and each year they find new ways to save money.

"It's real success has been showing students that they can take what they learn in the classroom and apply it to the real world," Slobe said.

They learned that a 75-watt incandescent bulb, very hot to the touch, wastes about 60 of those watts in inefficient heat energy. The spiral fluorescent bulbs are several times more efficient.

The toasters, microwaves, stereos, TVs — all carry a "phantom load" of energy usage even when they're not doing what they were built to do, but merely beaming the time or idling, they learned.

"Connecting all the parts was extremely challenging, but worth it," said eighth-grader Ally Meyer. "This makes you realize how much you can control.

"I already found out that my family saves $175 a year because we switched from incandescent bulbs to compact fluorescent."

The eighth-graders are well-versed in the Kill O Watt, a device that precisely measures the watts put out by an appliance.

Twenty-five of the students are bringing the Kill O Watts home to audit their own houses and find out where their families can save money.

Boulder Valley School District pays some $5 million a year to heat and light its 55 schools and other buildings, says Ghita Carroll, the district's new sustainability coordinator.

Part of a $300 million bond issue is dedicated to making energy improvements in all the schools, Carroll said.

"We have a lot going on, but it's been pretty fragmented," Carroll said. The goal is to get a handle on how much energy can be saved district wide then take a coordinated approach to it.

So far, BVSD has replaced lights through the district with more energy-efficient bulbs.

"We're replacing boilers with much more efficient boilers," she said. "We're doing energy tune-ups."

Carroll listened to the presentations on electricity loss at Monarch last week. "I was impressed that the eighth-graders were thinking about this," she said.

Recently, the state auditor estimated that $4.5 billion is needed to bring Colorado's public schools up to date — a figure that includes general renovations and replacing crumbling schools, as well as becoming more energy efficient.

Last year, the Colorado General Assembly passed the Building Excellence in Schools Act which allots $500 million to help school districts update buildings. The carrot of state matching funds can help the districts convince local voters to say "yes" to bond issues, said Ted Hughes, the director of capital construction assistance for the Colorado Department of Education.

Many schools were built more than a half century ago, when the norm was to put in huge, inefficient boilers Hughes said. "No one was thinking about energy costs then," he said.

The cost of changing out lights in the schools — from incandescent to compact fluorescent — can be recouped in just five years, he said, as way of example.

A bill passed in 2007 requires any school district project that gets a quarter of its funding from the state meet a high-performance energy standard, Hughes said.

"There is more and more awareness out there," Hughes said. "A lot of it springs from common sense but it is also driven by the governor, who is passionate about it."