Air conditioning & homes

Air conditioning condenser unit newerBack in the 1960’s, when I was growing up in Santa Clara, air conditioning was considered a luxury. I didn’t know anyone who had it in their homes in the immediate San  Jose area.  Hot days often weren’t too terrible, and if they were, we’d find our way to a pool, the beach, or an eatery with A/C.  Besides, locals would insist, “it’s a dry heat“.

Over the last few decades, though, central forced air conditioning has become mainstream.  I do believe that Silicon Valley has grown hotter in recent years and it’s less and less of a reasonable option to go without it for most home buyers.

How common is air conditioning in Silicon Valley?

Today I looked on the multiple listing service to get a sense of how common central air conditioning is in Silicon Valley homes. Here’s what I found:

Single family homes or houses for sale in Santa Clara County (home to about 1.9 million people) = 1408
Of these, houses with central forced air conditioning = 891 (63%)
Houses with central forced air – gas (could be overlapping with the group above but if combined it’s 1010) = 119
With ceiling fans = 254
With wall or window units = 4
With whole house fan = 33
No cooling of any kind = 298

Interesting to see that 21% had no fans or other type of cooling at all and that at least 63% but possibly as much as 72% do have central forced air.  If you are house hunting in the San Jose area, it’s important to realize that at least 25% of the homes on the market will not have A/C. 

How necessary is air conditioning in the San Francisco Bay Area?

This has always been the old debate: do we really need air conditioning?  In places like San Francisco and Santa Cruz, which are right on the ocean or bay, often the cool breezes make A/C absolutely unnecessary.

The further inland you go, the more important having it becomes. This is true both for the coast and the areas closest to the San Francisco Bay.  Morgan Hill and Gilroy, in “south county” are far from the SF Bay and from the Monterey Bay.  They get very hot in summer, and having a cooling system is an absolute must.

If you live in Redwood Shores or Foster City, which jut into the San Francisco Bay, it’s quite a bit cooler. Perhaps it would be a waste of money there to make that home improvement. Los Altos can be 5 or more degrees cooler than Los Gatos because it’s closer to the water. Even in Los Gatos, though, there are many micro-climates.  Downtown may get strong coastal winds bringing fog from the coast, while little valleys or areas tucked behind hills can be warmer and completely calm.

How hard is it, and how expensive, to add air conditioning?

Most of the houses here are served by central forced air heat, and they have ducts for this already.  If the furnace is younger, and if it is pre-plumbed for cooling, it may be simple and not too expensive (possibly around $5000 – $6000 but it depends on many factors, including home size).

It can be more expensive if:
-The furnace is older and needs replacing
-The electric panel is not sufficient – it may be necessary to add a sub-panel
-The condenser is a slim-line unit rather than a standard one
-If your house has radiant heating, electric baseboard or otherwise does not have central heating with ducts, the cost goes up very substantially.

It is always wise to take a few bids and to insist that your A/C contractor make sure that you get both permits and finals when adding it.

Many people with air conditioning find that they can run it much less by using a whole house fan and / or attic fans.  These are substantially less costly to operate, so having both can keep the power bills more reasonable. (That’s what we do at our house.)