The 60s - 7,793,000;

The 70s - 22,515,523;

The 80s - 31,547,042;

The 90s - 49,171,426.

In other words, there was seven-fold growth from the 1960s to the 90s.

As a subset of unitary products, heat pump shipments (and their share of the total unitary) through the decades look like this:

The 60s - 722,209 (9%);

The 70s - 2,571,854 (11%);

The 80s - 6,979,389 (22%);

The 90s - 10,118,580 (20%).

More significantly, this decade-long growth was accomplished against the background of two massive challenges to the air conditioning industry. These were the introduction of NAECA efficiency standards in 1992, which set a minimum level of 10 SEER, and the phaseout of CFCs under the Montreal Protocol.

Both challenges involved government-imposed - and very expensive - engineering changes to the industry's products.

Other types of A/C

Within the unitary category are nonresidential units, those 65,000 Btu and higher, which achieved a sixth record year with a 6% gain, according to the Air-Conditioning and Refrigeration Institute (ARI).

Other air conditioning products also showed a strong performance last year. Reciprocating chillers, clocking in at 15,385 units, saw a 3% gain. Also ahead for the year were central-station air handlers, room fancoils, icemakers, water coolers, heating and cooling coils, and variable air volume units, according to ARI.

There is nothing on the horizon to suggest any dampening of this strong growth in 2000. This January saw shipments of 433,386 units, up a whopping 25% over the January 1999 figure. Within this figure are 94,642 heat pump shipments, up 11%.

The industry enjoys growth in two broad markets. New single-family homes absorbed 1 million central air conditioners for the first time last year, and housing starts are on a path to equal or better last year's performance.

And with each year adding new air-conditioned homes to the building stock, at least 3 million replacements are completed annually.

Decade's shipments

The past decade also saw the shipment of 35 million room air conditioners, according to the Association of Home Appliance Manufacturers (AHAM). This is the first 10-year period in which shipments of this product did not exceed those of unitary products.

This continues to be a very volatile product, based largely on "impulse" sales from heat waves and sold mainly through appliance stores.

Last year, a record 6.1 million units were shipped in the same decade that saw a low of 2,820,000 units, a nearly three-fold swing.

This is a decade-by-decade summary of room unit shipments:

The 60s - 11,240,000;

The 70s - 29,265,000;

The 80s - 35,126,000;

The 90s - 35,000,000.

Already for the Jan-Feb period this year, shipments of 817,000 units are 31% better than the same period in 1999. In the long term, room units will decline against unitary products.

The replacement market consists of 31 million households that represent about 51 million room units. As the housing stock continues to grow, fewer newly completed homes will have room units vs. whole-house air conditioning.

Also absorbing these units are small commercial establishments, lodging, and institutional buildings.

Heating sector

Last year's shipments of gas-fired warm air furnaces, the main heating system in U.S. homes, totaled 3,126,127, a 5% increase for the year and the best year for the decade. Average shipments for the past 10 years were 2,056,000.

Most of these units go into new single-family housing, where they enjoy an 80% saturation.

Shipments of oil-fired furnaces, traditionally less than 10% of gas-fired units, ended the year at 125,378, a decline of 2%, according to the Gas Appliance Manufacturers Association.

GAMA also reported shipments of 200,893 gas boilers, up 9%; 128,645 oil boilers, up 1%; 35,927 vented room heaters, up 6%; and vent-free room heaters, up 3%.

The association also tracks vent-free gas logs and fireplaces, which were generally ahead of 1999. Here is the record: vent-free gas logs, 305,325, up 16%; vent-free gas inserts, 6,038, down 14%; vent-free gas fireplaces, 122,292, up 24%; and vent-free gas stoves, 24,000, up 28%.

A related product, commercial water heaters, also showed gains. GAMA tracked 100,701 gas water heaters, up 6%, and 39,845 electric water heaters, up 12%.