Tim Cobb, a boiler operator at Eastern Maine Medical Center, sat at his desk Tuesday and looked through a large glass window at a jungle of gleaming white tubing, concrete and enormous gray metal bins. He pointed to his computer screen as it flickered recordings of the temperatures and input and output figures of each machine.

“This is where it all happens,” said Cobb. From his tiny office, he controls EMMC’s new 3,400-square-foot combined heat and power plant.

The $8.4 million plant, under construction since August 2005, has finally been completed. It stands on the east side of the hospital complex between State Street and the Penobscot River.

The 4.6-megawatt facility is expected to supply nearly all of the hospital’s electricity, heating and cooling needs and reduce its dependence on the region’s commercial electricity supplier, Bangor Hydro-Electric Co.

For the past six weeks its four operators have been running tests on natural gas and oil to determine which is the less expensive and more environmentally friendly fuel.

“Right now it looks like we’ll go with natural gas,” said Paul Jellison, plant supervisor.

“It burns so much cleaner,” added Jeff Mylen, director of special projects for EMMC.

On a tour of the facility Tuesday, Jellison opened what looked like two enormous refrigerator doors to expose the deafening noise and impressive sight of a combustion turbine similar to a jet engine.

The turbine has a compressor to draw in and compress air; a combustor, or burner, to add fuel to heat the compressed air; and a turbine to extract power from the hot air. Hot gasses go through a heat recovery steam generator and the steam is sent to the hospital to heat the building, its water and operate its laundry and sterilizing equipment.

The turbine will produce up to 4.6 megawatts of electricity continuously, enough to run 46,000 100-watt bulbs.

When Jellison closed the doors to the turbine, the noise was reduced dramatically.

“We took sound very seriously on this project. It was designed so that you could have a normal conversation five feet from the building without hollering,” Mylen said. And indeed, you can. The turbine is surrounded by insulated walls and the building itself was constructed with reinforced concrete.

The finished plant measures 100 feet by 35 feet and stands 35 feet tall. Cianbro Corp. of Pittsfield, the project contractor, also built a 500-ton steam absorption chiller, two 15-foot cooling towers and a 95-foot emissions stack. Boston-based Vanderweil Engineers designed the facility.

The project cost $8.4 million, $3 million of which was paid for by Oak Ridge National Lab, a contract administrator for the federal Department of Energy. EMMC expects to save more than $1 million in energy costs annually and expects the project will pay for itself in 4.9 years. Mylen said the hospital, over the past year, paid Bangor Hydro $2.8 million in electric bills.

This savings will be passed along to patients, Mylen said, but there is not yet any estimation of how much bills might decrease.

“Our primary reason was to reduce health care dollars,” Mylen said. “It was our due diligence to put this in.”

Bangor Hydro contested the project at a public hearing in September 2005 on the grounds that it would drive up the cost of electricity to other consumers in the region by $800,000 a year. Now that EMMC plans to rely on Bangor Hydro at least as a backup power source, that figure may change.

“It’s still rather uncertain as to how much the cost will go up,” said Andrea Littlefield, a communications officer at Bangor Hydro. “It’s really hard to tell in that they’re still on our line.”

The hospital has maintained that in addition to reducing costs, the generator would serve as a backup system to avoid catastrophe in the event of a power outage, such as the one caused by the ice storm of 1998.

If the plant has to be shut down temporarily for repair, it will import power from the regional distribution lines, Mylen said. During summer months, when there is greater demand for electricity, the plant will import Bangor Hydro-supplied electricity for air conditioning.

The plant has an agreement with Bangor Hydro that does not allow the plant to export energy, Mylen said.

“We will still be a customer of Bangor Hydro,” Mylen said. “We did this not only for economic savings; it has increased our reliability many times over.”