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 a restaurant, library, or theater with A/C.  Besides, as locals would insist, “it’s a dry heat”.

Over the last few decades, though, central forced air conditioning has become more 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) = 743
Of these, houses with central forced air conditioning = 457 (61.5%)
Houses with central forced air – gas = 0
With ceiling fans = 121
With wall or window units = 18
With whole house or attic fan = 17
With multi-zone cooling = 88
“Other” cooling listed = 28
No cooling of any kind = 172 (23.1%)

There may be overlap in some fields. Interesting to see that 23% had no fans or cooling listed at all and that at least 61.5% but possibly as much as 66.5% (if including multi-zone and “other”) do have central forced air.  If you are house hunting in the San Jose area, it’s important to realize that at least 23% of the homes on the market will not have any A/C. 

And from 2016:

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 (21.1%)

In just 7 years the percentages of homes listed for sale with central A/C or with no cooling haven’t changed much, however we are seeing more homes with alternative cooling advertised. This may indicate an increase in buyer interest in this feature.

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

This has always been the old debate: “do we really need air conditioning?” Like many things, that depends. microclimates can have a huge impact on weather.

Skyride in foggy Santa Cruz

Skyride at the Boardwalk one foggy Santa Cruz morning.

In places like San Francisco and Santa Cruz, which are right on the ocean or bay, often the cool breezes, foggy mornings, and more stable temperature of the water make A/C absolutely unnecessary.

Further inland areas may experience more severe summer heat, and the more important having A/C becomes. 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 microclimates. 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. We live in East Los Gatos and often it will be raining on one side of Blossom Hill, and sunny on the other!

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

Most of the houses here are served by central forced air heat, with ducting supplying heat to the rooms and an appropriate return, and this system can be used for cooling as well.  If the furnace is younger, and if it is pre-plumbed for cooling, it may be simple to add 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 nonstandard, such as a slim-line unit
-If your house is not already ducted, such as homes that are heated through radiant heating systems, electric baseboard, wall units, or otherwise, 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.

Thankfully because we do tend to have a “dry heat”, many people with air conditioning find that they can run it less by using a whole house fan and / or attic fans when the weather is cool and pleasant in the mornings and evenings. 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 unless the air is bad. Our A/C has been a huge boon during fire season.