ETOWAH, Tenn. - How many workers does it take to change the light bulbs in an industrial plant?

To design and replace 3,180 fixtures at the biggest electricity user in McMinn County, it took eight experienced contract employees working around the clock for 60 days.

But the newly completed lighting system at the Johns Mansville fiberglass plant here is quickly paying off.

Acumen Energy Solutions, the Overland Park, Kan.-based contractor that installed the new energy efficient lights, estimates the changes should cut the plant's light bill by 70 percent, or enough electricity to power 300 homes. The energy usage drop also cuts the plant's indirect annual carbon dioxide emissions by more than 6 million pounds.

"No pun intended, but this is a very visible project that shows our commitment to sustainability, saving money and reducing our emissions while making a better working condition for our employees," said Michael Lawrence, senior vice president and general manager of engineered products for the Denver-based Johns Manville Co.

Such changes at 16 Johns Manville facilities across the country should cut the company's energy bills by $2.5 million, providing a payback on the company's $8 million investment in less than three and a half years.

An even faster payback came Wednesday when the Tennessee Valley Authority gave Johns Mansville a check for $343,410 as a rebate under the utility's EnergyRight Solutions program. The JM facility here is one of 114 completed projects in the Tennessee Valley -- and another 203 energy efficiency projects at other businesses under way -- that are sharing in $20.6 million TVA budgetted this year to encourage energy savings initatives by industry.

Wayne Scarbrough, assistant general manger for Athens Utility Board, said such savings will cut what Johns Manville pays to the local power distributor "and may make us redo some of our budget."

But Scarbrough said the most important goal is to keep area businesses competitive and reducing or limiting energy costs is vital if local industry is to remain in business.

Many utilities are offering industrial customers rebates to help pay for energy efficiency upgrades. Nationwide, Johns Mansville is getting $1.5 million in rebates from utilities with industrial efficiency reward programs.

Such energy demand programs help limit the need for TVA and other power producers to have to build new, and usually more expensive, generation.

The U.S. Energy Information Administration estimated that in 2011, the total electricity consumed in lighting buildings across the U.S. was about 12 percent of total U.S. electricity consumption. If the country could follow our Etowah plant's leadership of a 70 percent reduction, it would account for nearly an 8 percent reduction in national electricity consumption."

In Etowah, as in the other JM facilities where similar projects took place, an initial audit was conducted, taking into account plant operating hours; traffic conditions in production, storage and warehouse areas; and lighting density requirements. Based on that assessment, almost all of the high bay HID fixtures, which were predominately metal halide, sodium vapor or incandescent lights, were replaced with more efficient and less energy-intensive fixtures.

"Energy efficiency has become an increasingly important part of TVA's mission to support both the economic growth and environmental health of the Tennessee Valley," said Odell Frye, general manager of TVA Customer Delivery for the Etowah area.

Much of the lighting efficiency here also comes from smart lights with sensors that automatically turn on or off when workers enter or leave a work area.

Lawrence said to stay competitive in its fiberglass and engineered products field, Johns Mansville "must continually improve our operations and products." The JM division was hard hit by the housing slump. While business has come back and the plant staff here is back up to 242 employees, business is still short of its pre-recession peak.

Johns Mansville purchased the former Beaunit Mills here in 1977 and started production of its glass and fiberglass products in 1979. The plant operates two furnace lines and makes fiberglass mats used as backing for roofing shingles and other fiber and glass products used for ceiling tiles, sheetrock and even some military equipment.

The 700,000-square-foot plant is on 100 acres just north of Etowah.