I'm in Chicago land and frankly you're not wrong. Solar is not that great. Until you add an electric car or two. My rates were awesome at 10.5c/KWh before solar and about 4.5c after. When you migrate $400/month in fuel cost to $200/month in New electricity cost, on top of the original $150/mo. Solar starts to look real good. Now I pay less than $100/mo. And that covers two EVs and my home. Net savings around $275/mo. $35k system, half paid for by invectives (Fed tax credits and srec program) leaves about $17,500/12 mo /$275 savings per month = just over 5 year pay pack. The system will generate for 25+ years and electricity rates always go up, so the long term value is more then $60k+ in total net payback even though there will be some degrading of production.
Elon was right. People will eventually understand why acquiring solar City was important and required.
Residentual solar is only a tiny part of the equation. Super and mega charging, if converted to solar and battery, would give Tesla a cost closer to 5c/KWh, allowing for 30% GM for megachargers. If all where converted, Tesla would instantly become the largest most profitable utility on the planet with a highly captive customer. Don't be fooled, Tesla does not have to put the panels on the chargers, they can work deals with utilities to provided offsets and energy in smart ways so that an equivalent amount of charging is offset by smarter grid tech. In theory, 50,000 solar + powerwalls could be used to offset supercharging for a large City, and much of the mega charging will be done at the customers distribution centers and where they unload at say a local Walmart. Tesla will install solar + battery in partnership with customers. And they will be happy to do it, because the batteries and solar will be used for then entire distribution hub or store and will save them even more then switching to Tesla semi alone.
Tesla's biggest issue today is not demand, it's opportunity loss due to but being able to expand fast enough. Model 3 is totally consuming every cell they can make. Semi will require 100GWh for 100k semis per year. That is almost 5x the cells they make today at GF1. Staying public was probably the only way to realistically get the funding required for this kind of expansion.