BOISE-- A Boise company's focus is on a resource deep underground, but it may just be scratching the surface of its business potential.

"We're always in hot water it seems like, but hot water for us is a good thing," said U.S. Geothermal, Inc. President and Chief Operating Officer Doug Glaspey with a grin. "This was a hayfield when we first got here in 2005. We drilled our first well in 2006," added Glaspey as he gestured from a hillside overlooking the company's Neal Hot Springs Geothermal Power Plant a few miles outside Vale, Ore.

It started producing power in late 2012.

"This is our largest project in the U.S. Geothermal company," said Glaspey.

It's longer than four football fields and produces about 22 megawatts of electricity every year. That is enough to power 24,000 homes.

Glaspey says they have a 25-year contract to sell electricity to Idaho Power.

The site has four production wells that pump 287-degree geothermally heated water from about 2,300 feet underground. The equipment also includes pipes, vaporizers, turbines, generators, and cooling towers.

"This is a 150 million dollar capital cost project here in this little power plant," said Glaspey.

The geothermal water is pumped to vaporizers that turn a refrigerant into a high-pressure vapor, the vapor turns a turbine, the turbine turns a generator that makes electricity, which is put on the power grid. Then, the now cooler, 150-degree geothermal water is pumped back into the ground.

As Glaspey explains, it's that last step that makes this a form of renewable energy.

"We put 100 percent of the fluid back into the Earth to be reheated and it gets reused again."

The refrigerant stays in a closed loop. It is cooled back into a liquid by huge fans in large towers called air cooled condensers.

The power produced here is not only renewable energy, but also green energy. "There's no carbon emissions," said Glaspey. "There's no CO2 emissions. No emissions of any kind come out of this power plant."

Glaspey says the main environmental concern is the fresh groundwater under the site. They monitor springs and wells in the area.

"Because geothermal brine tends to have a little bit different mineral composition than fresh water, we could tell immediately if we were breaking through into that ground water," said Glaspey.

Glaspey founded U.S. Geothermal in 2002. "It's just part of what's driven me my whole career is creating something out of nothing."

At the corporate headquarters on Park Center Boulevard in Boise, Chief Financial Officer Kerry Hawkley told KTVB he joined the company in 2003 when all it had was "some dirt and a dream."

Now the company has three operating plants; Neal Hot Springs, Raft River near Burley, Idaho, and San Emidio, Nev. Combined, they produce 45 megawatts. That is enough electricity to power about 50,000 homes.

"We're kind of one of the last of the small geothermal companies. We survived by just being very conservative," said Hawkley.

Hawkley says U.S. Geothermal employs 49 people. According to its year-end financial report, in 2016 the company had revenue of $31.5 million and net profit of $5.2 million.

It is still a small business, but primed for growth. It has projects under development in California, Nevada and Guatemala.

"If we can get to 150 megawatts in the next two to three years, we'll have really accomplished something," said Hawkley.

Both Glaspey and Hawkley believe geothermal has immense promise.

While the water does gradually lose temperature over time as they pump it out and back in, they think technology will keep up with it.

"In 25 years from now we may find there's a new technology that can take that colder fluid and still keep generating power just as efficiently as we're doing today," said Glaspey.

"What we're doing is we're mining heat from the center of the earth," said Hawkley. "That heat is going to remain there as long as we exist."

"I think it's fair to say that in the United States today, and in most of the world, everybody's interested in renewable energy," said Glaspey. "They want renewable energy, and of course, we want to give them that renewable energy."

Glaspey also says the equipment at the Neal Hot Springs plant outside Vale is 95 percent American made.

U.S. Geothermal is a publicly traded company (NYSE MKT: HTM).