You assume that power use is constant during day/night. It is not and does not have to be. Also, as far as cost of generating concerned, PV have reached the parity already, so, it's done and not a factor anymore. The only problem is cost of batteries and to cover for night use you need 20kwh battery per person which costs $1 per w*h (current prices for lithium batteries), so it will cost you $20K. That battery with careful use will last 10 years. so it's $2K a year for 100% solar electricity, no nukes, no coal, no gas turbines.And no, there is no miracle battery technology that will change this equation. The current best battery technology, LiFePO4, costs more than three times more than the PV solar panels over the lifetime of the system. And PV panels have only just reached cost parity with coal on a kW basis but they can only generate at full capacity for eight hours a day meaning you have to have 2.5 to 4 times the PV generated kW installed to replace coal and nuclear with power storage of 1.5 to 3 times the kWh of storage. These numbers have to be on the higher side to allow for cloudy days and at this, it wouldn't negate the need for a full fossil fuel back up and a dramatically beefed up power distribution for the US. This is frightfully expensive.
This is a worst case scenario calculation using off the shelf batteries costs, current electricity use and being constant throughout 24 hours.
In reality everything can be improved without much effort by simply not wasting electricity by a factor of 2 at least. The only limiting factor is amount of lithium, but it's not the only element which can be used for batteries and it's not consumable.
Epic failure.
Yes, PV costs about as much per watt. However, the sun doesn't shine all the time, you're looking at a very poor duty cycle--20% is about the best you'll get in most places. That's going to increase your costs something like 4x.
Second, your 20 kwh of storage suffices for overnight in places where you don't use all that much power. A rainy day and your lights go out. You're going to need to considerably increase your storage and thus your cost.
There's also the efficiency of the storage, I'm not finding much data but I did run into the figure of 80%--which means increasing your PV array by another 25%.