In midsummer, a householder's fancy turns to keeping cool. Some renters and owners rely on a combination of whole-house attic fans and oscillating table-top or window-mounted models. Others perform the annual rite of installing clunky window-mounted air conditioners.
In much of the country central air-conditioning has become standard in new homes. Fully 99 percent of new homes built in the South today come equipped, according to the Air- Conditioning and Refrigeration Institute (ARI). Overall, nearly 60 million US households had central air in 2001, according to the US Energy Information Agency.
Nationally, shipments of central air systems have nearly doubled since 1992, the last time the government nudged up efficiency requirements in the form of minimum SEER rating (for Seasonal Energy Efficiency Ratio), the measurement of the unit's cooling and energy efficiency. The increase then was from eight to 10.
Efficiency standards for systems sold in the US are set to change again Jan. 1, 2006, with a boost to a SEER 13 minimum for all units sold in the United States. That leaves current system owners - most of whom are oblivious to SEER, according to a recent industry survey - with a new factor to consider in a repair- or-replace calculation.
It's not a simple one, if you listen to all of the industry's voices. Waiting for next year's models is either a reasonable plan, given the resulting energy savings over time and the industry's history of bringing prices to heel. Or it's a formula for incurring huge upfront expenses - including the cost of hiring building contractors - that will be difficult to recoup.
About 8 million central-air systems are sold each year, with some 70 percent of those sales in replacement units. Replacement becomes an issue sometime after a decade of use.
The timing of unit replacement and its impact on price isn't something that most owners think about.
"Most consumers don't understand that there are going to be cost differences, so they only react when something breaks," says Karl Zellmer, vice president of air-conditioner sales for Emerson Climate Technology. "If it breaks now they have options down to 10 SEER, which is the minimum, and if it breaks a year from now it's going to be 13 SEER, and it's going to be a higher cost."
One contributor to the cost hike: unit size. This is not an area of consumer technology in which modern translates to slim. New units can take up as much as 40 percent more room. More refrigerant requires more coils, inside and out, so modifications could be required throughout a home. Outside, poured concrete slabs prepared for current home models might be inadequate for post-2006 units.
"If the equipment is more than 10 years old and [an owner] is starting to have difficulties with it, they might want to look into replacing it this year, even if it hasn't failed yet," says Glenn Hourahan, vice president for technology at Air Conditioning Contractors of America.
Still, trading up in terms of SEER has its advantages. Mr. Hourahan says the jump from 10 SEER to 13 will lower an energy bill by about 25 percent on average. Emerson's Mr. Zellmer maintains that a jump from an old 8 SEER to 13 translates to 62 percent more efficiency.
Estimates on the cost of new units are even more difficult to pin down. A central-air system can run anywhere from $3,000 to $10,000, according to Hourahan. He says prices for the new systems are likely to jump by 20 to 30 percent.
But others insist that leading manufacturers already have the SEER and size issues under control, and that competition will corral prices fast.
"Trane is now selling a SEER 19 air conditioner; Lennox also has a SEER 19 unit," according to Kit Kennedy at the Natural Resources Defense Council, which has pushed the Bush administration to raise minimum standards. "So they'll continue to differentiate on SEER levels as well as other features to capture the premium market."
Manufacturer Bryant already has a SEER 13 unit that's 20 percent smaller than its older model, adds Harvey Sachs, director of buildings programs for the private American Council for an Energy-Efficient Economy (ACEEE), who is also optimistic about costs.
"If you were just predicting [based on history], your best guess would be that SEER 13 products, say two years after they go into effect, will be the same price as SEER 10 is this year," he says. Increases in the costs of copper, steel, and aluminum might push that timeline out a bit, he adds.
Close to 90 percent of any manufacturer's units are produced at the base federal efficiency requirements, explains Sachs, so those are the units on which makers lavish their best design and production practices. SEER 13, he says, will very quickly become cost-effective.
"In 1992, when the 10 SEER standard was issued, prices did drop after the first two years," acknowledges Joe Stevens, a spokesman for the Air-Conditioning and Refrigeration Institute, the industry trade group.
Important for consumers, all experts agree, is caring for whatever system you have. Regularly maintained, a system should last close to the 20-year mark, says Mr. Stevens.
"If you have an AC that's seven or eight years old, and you do annual maintenance on it for the heating and cooling seasons, that will ensure that it operates as efficiently as when it was new," says Hourahan.
"The most important consideration is finding a contractor who is willing to spend the time to size equipment properly and install it with quality," says Sachs. "There's much more variability in installation quality than there is difference between SEER 10 and 13."