In a traditional building, a boiler will kick on at a set outside temperature and keep supplying heat, even if the inside temperature is within a normal, comfortable range. But several companies provide systems and technology to balance the heat in a building, primarily by installing some wireless sensors that can read the inside temperature. If a sensor in one part of a building reports inside temperatures below or above a set level, a computer sends a signal to the nearest riser to increase or decrease heat there.

At The Schwab House co-op on Riverside Drive in Manhattan, for instance, board treasurer Mitchel Levine says that because of such technology his building "will actually spend less in today's dollars on heating oil than we spent in 1982." He credits energy-efficiency measures that his board enacted for years, but says a key move came about two years ago when the co-op paid $125,000 to install the Energuard climate-control system to balance the heat distribution.

In 1982, the building bought 509,000 gallons of heating oil. Levine projects the property will use only 220,000 gallons in 2007. Think of it this way: The No. 6 oil used by The Schwab House runs about $2.15 a gallon. If the co-op had had to buy the former amount of fuel oil, it would have had to spend about another $500,000. And since apartments close to Riverside Drive — and the wind off the Hudson River — tend to colder than others in the building, the system is be programmed to send more heat in that direction. So aside from saving money, Levine says, the system allows the building to operate more effectively for residents' comfort and "deliver the heat where it's needed."

U.S. Energy Group provides a heat-balancing system called the Energy Management System (EMS) to about 2,000 buildings citywide. "Operating a building without an EMS is like driving a Hummer in Manhattan traffic," says Warren Zaretsky, the company's vice president of marketing. "It's just wasteful."

U.S. Energy Group provides a heat-balancing system called the Energy Management System (EMS) to about 2,000 buildings citywide. Wireless sensors in apartments communicate to a device on the boiler, telling it to kick on if the inside temperate is below a set level or to cut back if it is above. EMS also places sensors inside key heating elements like the chimney stack and boiler coils in order to provide preventive-maintenance data.

Warren Zaretsky, the company's vice president of marketing, estimates it costs between $8,000 and $10,000 to install EMS in an 80-unit building. The company guarantees that a building will save at least 15 percent on its fuel consumption. "The return on investment is almost always less than two years," he says.