1. Are houses in SF well insulated?

2. 40°F is 4°C. That's cold. What do you expect the indoor temperature to be in those conditions, without heating?

While I suspect 1. to resolve false, I wish to offer anecdote about what's possible:

I'm currently living in a well insulated German new build, and over this last winter was wearing a T-shirt inside while it was actively snowing outside. The average combined power consumption of all things in this property is about 500 watts. It would be lower, but we didn't know how to correctly configure some of it in the first 6 months.