Castro Valley AC & Furnace Install
done today, done right.

California licenses this trade as a C-20 — warm-air heating, ventilating and air-conditioning. In the Contractors State License Board register for Alameda County, 8 active C-20 licences give a Castro Valley business address as of 2026-09-02, out of 260 across the county. That is a middling bench — enough choice to be selective, few enough that the good ones are booked solid in the first heatwave.

5 hold the C-20 on its own; the other 3 also carry a general building or plumbing classification. A C-20-only shop does this work all day, which is worth knowing when two quotes look the same on paper.

By business structure the Castro Valley list runs 4 sole owners, 3 corporations, 1 limited-liability company. Sole owners lead the list, which usually means the person who quotes the job is the person who does it.

Those addresses sit in 2 ZIPs: 94546 (7), 94552 (1). 94546 alone accounts for 7 of the 8. We cover all of them.

CSLB issues licence numbers in sequence, so the register doubles as a record of how long the trade has been established here. The longest-held active C-20 in Castro Valley is number 603913; its newest is 1145723. Across the whole county the range runs 68847 to 1159177, so Castro Valley's oldest surviving licence sits in the middle of it — an established local trade without the county's oldest names.

That register is how we decide who gets your request: an active, unexpired licence, and a preference for the C-20-only shops. 3 of the Castro Valley licences come up for renewal before the end of 2026, and a lapsed licence is uninsurable — one more reason to check the number rather than the van. Check ours, or anyone's, yourself — every California licence is public at the CSLB licence lookup. A contractor who will not give you a licence number has told you what you need to know.