Given how popular Tesla is and will continue to be in CA as the Model 3 ramps up, even if only electric car owners in CA order the Solar Roof v1 in the next three years, that would more demand than Tesla can supply: 25k in 2017, 50k in 2018, and 100k in 2019, by my estimate.
Cost of electricity is a win-win for Tesla: if it goes up, they win on the energy generation side; if it goes down, they win on the energy consumption side. I think, net, Tesla would benefit more if the cost of electricity declined since the Automotive business comprises a much larger percentage of revenues and future profits.
I agree that most all-electric car owners will opt for solar at some point, but I'm not sure if Tesla will be able to ramp up Solar Roof production quickly enough to realize your projection. They would need to exercise the option to expand Gigafactory 2 to 5 GW. Do you have an estimate of the cap-ex required to do that?
500,000 Solar Roofs per year would bring in ~$40B in revenue and at 20-25% gross margin $8B-10B in gross profits per year. If the demand is there, it would make sense to spend up to $5B to pull forward Solar Roof production, but Tesla would need another capital raise. Also have to ask, are those dollars better spent on the energy consumption (i.e. automotive) side? Or utility-scale energy storage side?
To me, Tesla seems to have a larger competitive advantage on the automotive side, so it may make sense to widen that moat, but I don't think Elon is thinking in those terms. From the mission statement perspective, it probably makes more sense to spend any additional dollars on Tesla Semi or utility-scale energy storage. I would appreciate some insight on this from those who are more knowledgeable in how much each of Tesla's segment contributes to lowering carbon emissions.