Coincidentally, a new rule requiring that room air-conditioners be 10 percent more efficient took effect on Sunday.

"If you replace a 15-year-old room air-conditioner with a new Energy Star model, you can save $50 or $60 a year."

A megawatt-hour is enough to run 1,000 room air-conditioners for about an hour.

Unlike most other appliances, room air-conditioners are heavily dependent on weather for sales.

Let us pause for a moment on the comparative virtues of the room air-conditioner.

By Aug. 1 American manufacturers had shipped more than 3.8 million room air-conditioners, up 20.6 percent from 1987.

Last summer, two room air-conditioners were installed at a cost of $400, with the library's trustees doing the work.

(One kilowatt-hour is enough to run a large room air-conditioner for an hour.)

The industry estimates that almost half of the new sales of room air-conditioners will be replacement units.

Purchasers of room air-conditioners have plenty to think about if they want good value.