If every mid sized+ city in the world started building one today, and it took 5 years to construct, and they started a new one every other year (so they were being built in parallel). The problem would be solved within a decade.
A year or so ago, I looked at the cost of South Texas Project in Texas, and how much power it generates and figured out that for roughly a single year's state budget one could build 10x those plants, which would remove all natural gas, and coal electric production in the state. Do it a second time, and there would be enough to actually move a significant part of the cars to electric too.
You would need ~1.4 million barrels of oil per day for 50 years.
edit: it is still weird to see Venezuela at the top spot and just how badly they squandered it
Projected is the operative word.
One useful concept that was introduced a decade ago is a "cubic mile of oil", or CMO. To yield the equivalent power, one would need to produce 250,000 roof-top solar systems a day for 50 years, or 1200 turbines a week for 50 years, or 1 nuclear power plant a week for 50 years. Innovation is still desperately needed here. Nuclear has been unfairly sluggish in this department.