I think it depends on local weather. We spend about $600 on electricity and $600 is gas per year for 4 people in the Bay Area. And this is with an older water heater and furnace in an old house with moderate insulation. We would replace the heater, furnace and improve the insulation before even considering solar ourselves.
+1 to first upgrading your home. I live in the Bay Area but in a tightly sealed late 90's 1600 sqft house. No A/C. Recently upgraded our furnace and water heater to high efficiency models, and now spend about $400/year electricity, $400/yr for gas. Even accounting for the warmer winter this year, the gas savings was about 14%. There are pretty good incentives in the Bay Area for home energy upgrades if you do multiple at once: https://www.bayareaenergyupgrade.org/program-overview
