I think you may be right. I would have thought 40,000 would be
enough for the bay area. But here's an online rough estimator
that says for 2,000 sq ft, you need 58,0000 OUTPUT btu. Assuming
95% eff, he'd need 61,000 btus.
Of course, this is just a rough estimate calculator, but I'd trust
it more than the shyster he's dealing with. Given the more
temperate climate, I'd also go with a two stage if possible so
that it can fire on low most days.
I don't know that there are any gas-fired furnaces at the 95%+
efficiency rating that are not multi-stage. The one in my old house
was 3-stage, and my new one has a 3-stage fan with a true variable
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