cricketo said:
Well, a couple of other options would be some clever long-term energy storage or shipping energy from the sunny parts via High Voltage DC transmission lines (very low losses).
OK let's run the numbers on the latter. A HV transmission line from Arizona (big generation potential) to New York (big load) would be about 2500 miles. A 600kV, 3GW transmission line costs about $1.6m per mile. Each substation costs about $500 million; presumably there would be about half a dozen on each line. This would be close to ideal since the peak draw in NYC (around 8pm in the summer) coincides with a time of reasonable generation in Arizona (5pm.)
New York City draws a peak of about 13 gigawatts on a hot day. Let's assume that's what we design for; that allows about half of that to feed nearby cities (Jersey City, Greenwich, Newark etc) during average demand times. That means 5 transmission lines for a total cost of 20+15=$35 billion. Without the generation, just for the transmission line. Also, since capacity factor will be about 20%, the lines will deliver a net of about 1/5 of their rated capacity on average, or about 3GW.
Let's compare that to a new nuclear reactor comparable to the Vogtle plant. Those will generate about 2.2 gigawatts average for a cost of $9 billion.
So what should we do? I say we do both. We build nuclear power plants for baseload power _and_ build HVDC powerlines to bring power from good solar areas to heavy loads. (And of course build the solar plants to feed the transmission lines.) Build the HVDC lines one at a time so we can learn from them while getting the nuclear power plants on line to drastically reduce CO2 emissions.
References:
https://www.wecc.biz/Reliability/2014_TEPPC_Transmission_CapCost_Report_B+V.pdf
https://www.coned.com/en/about-us/corporate-facts
https://en.wikipedia.org/wiki/Vogtle_Electric_Generating_Plant#Units_3_and_4