Air-conditioning: Our Cross to Bear

When it's hot and humid out and the air-conditioner's not running, America suffers. Babies break out in rashes, couples bicker, computers go haywire. In much of the nation, an August power outage is viewed not as an inconvenience but as a public health emergency.

In the 50 years since air-conditioning hit the mass market, America has become so well-addicted that our dependence goes almost entirely unremarked. A/C is built into our economy and our culture. Stepping from a torrid parking lot into a 72-degree, air-conditioned lobby can provide a degree of instantaneous relief and physical pleasure experienced through few other legal means. But if the effect of air-conditioning on a hot human being can be compared to that of a pain-relieving drug, its economic impact is more like that of an anabolic steroid. And withdrawal, when it comes, will be painful.

We're as committed to air-conditioning as we are to cars and computer chips. And a device lucky enough to become indispensable can demand and get whatever it needs to keep running. For the air-conditioner, that's a lot.

The costly care and feeding of AC

Like a refrigerator, an air-conditioner works by piping a chemical refrigerant through cycles of compression and expansion. The refrigerant absorbs heat from cool interior air and releases it to the hot air of the great outdoors. In doing so, it's impeded by the Second Law of Thermodynamics, or Entropy Law, which says that temperatures tend to even out -- that heat naturally flows from a hot to a cold area. So an air-conditioner has to mechanically compress the gaseous refrigerant into much hotter liquid form and pump it through outdoor coils from which it can release the heat it has absorbed. To do that requires a lot of energy, usually from a power plant or a vehicle engine.

Almost one kilowatt-hour of electricity out of every five consumed in the United States in a full year goes to cooling buildings. Much of the nation's excess power-generating capacity, which sits idle until needed to satisfy quick spikes in demand, has had to be built because of air-conditioning.

The electricity used annually to air-condition America's homes, stores, offices, factories, schools, churches, libraries, domed stadiums, hospitals, warehouses, prisons and other buildings (not including what's used to cool manufacturing processes and military facilities) exceeds the entire electricity consumption of the world's second and fourth most populous nations -- India and Indonesia -- combined.

The refreshing air that comes out of an air-conditioning system has an evil twin: carbon-laden exhaust from the utilities that power it. Just about 50 percent of U.S. electricity is generated with coal; 21 percent with other fossil fuels, mostly natural gas; 20 percent with nuclear fission; less than 7 percent with hydroelectric dams; and about 2 percent with biomass, wind and solar methods combined. Coal is the worst carbon dioxide producer, but all of those methods generate greenhouse gases and other ecological hazards during construction and operation.

In January, the Environmental Protection Agency (EPA) raised energy-efficiency standards for newly manufactured home central air-conditioners by 30 percent. Central air units typically last 15 to 20 years, so the new regulation will have little effect in the near future. Even if all units were replaced overnight, it would mean less than a 5 percent reduction in the power that's used to air-condition buildings. That's because the new rules don't apply to window units or to nonresidential air-conditioning.

The average household in the southeastern United States consumes almost twice as much electricity as the average household in New England, but air-conditioning doesn't account for that entire disparity. Southerners use a lot more power for all appliances, whatever the season. Of course, northern households consume more fossil fuel for heat, but in the dead of winter, heating cannot be dispensed with.