There's another large effect that is left out of this story. As solar gets cheaper, and as we get more of it, it reduces the marginal pressure on fossil fuel production. That, in turn, makes fossil fuels cheaper and forces solar to get cheaper still to compete.
Solar doesn't much compete with petroleum. Its main effect is to reduce prices for coal. You'd expect that this might start to affect the profitability of coal companies eventualy....
For solar to affect petroleum, whose primary use is transport, we'll need to solve the storage problem. Tesla notwithstanding that has not happened. Electric vehicle sales were 0.66% of unit auto sales in 2015, and actually represented a sharp numeric decrease from 2014.
(The dollar volume is higher given the higher price of electrics, but it's unit sales you want to watch.)
Once you've got electricity, FT appears to win. Though again, there's the ages of investigation without large-scale application, on a power-to-fuels basis.
Sasol, the South African energy company, did run commercial coal-to-liquids via Fischer-Tropsch, since the 1950s, and I believe may still do so. The US tried but ran into technical issues.
