Big drills roared at Northview Heights last week, their truck-mounted bits boring 300-foot-deep wells in the rocky earth, seeking neither oil nor gas, but only access to the subterranean temperatures that promise to warm, cool, and save money.

The drilling of geothermal wells is part of the transformation of the 501-apartment Northview, plus its 91-unit high rise, into models of energy efficiency.

Eventually, the Pittsburgh Housing Authority's 3,300 occupied apartments, plus 200 that are now empty, will get an energy overhaul. It's a $25 million project run by Minneapolis-based Honeywell that involves everything from weatherstripping to new refrigerators, and is guaranteed to pay for itself.

"It's going to be better for the community, and better for the quality of living," said Patricia Bagley, a Housing Authority board member and Northview tenant leader. "It's something to look forward to for the future.

"Some people don't like change," she added, but her residents understand it.

"What it does for Northview, is it gives it more marketability," said authority Executive Director A. Fulton Meachem Jr. "It gives them central heating and air. They never had that at Northview."

Perhaps the most dramatic change in Northview, Homewood North and Arlington Heights will be the drilling of 5-inch-wide geothermal wells near every building, and installation of heating and cooling systems that use them.

In the summer, heat pumps will transfer the warmth from the air into water, which will then flow through underground tubes into the wells. There, the earth's near-constant 55-degree temperature will cool it, and it will flow back to carry off more heat. The resulting cooled air will be pumped through a central air system that will replace the inefficient window units that are now prevalent in public housing.

In winter, the comparative warmth the water carries from the earth will be used to heat the air.

In the three public housing communities, the entire system will be quiet and hidden, the heat pumps in enclosed parts of buildings, and the tubes covered by landscaping.

Combined with new thermostats that don't allow the winter temperature to be set above 73, or summer settings below 75, it should lower energy bills and provide a more regular climate for residents used to uncontrollable furnaces and struggling window units.

"That is the whole idea: Being able to make them more comfortable, and do it in a way that saves the Housing Authority money," said Ron Blagus, energy market director for Honeywell Building Solutions.

Honeywell guarantees the authority $3.2 million in reduced utility bills annually for at least 12 years, more than covering the up-front cost. About one-quarter of the savings is attributed to the geothermal wells. The rest comes from changes like insulation, efficient light bulbs and refrigerators, and reduced-flow toilets, tubs and sinks.

The flow reductions aren't popular. "It takes forever to fill the bath tub, or the sink for dishes," said Renee Simpson, a 15-year resident of Northview, as she waited for the bus to take her to her job as a security guard.

But the improvements contribute to a sense of progress in a community long known for gang trouble. "I've been seeing a lot of positive change up here," Ms. Simpson said.