"a hundred miles square" means 100 x 100 miles, 10,000 square miles. The linked article makes this clear.

At $250 per square meter, 10,000 square miles of panels would come to $6.4 trillion.

I think we should be heading in this direction anyway. But it's not so small, it's not so cheap, it will take time. No surprise; the system we need to replace is not small or cheap, and it took time, too.

>I feel like if it were as easy as a 10x10 mile plot of solar panels to power the entire US, some enterprising disruptor would have done it already. Think of the revenue from powering the entire US...

Solar is expanding rapidly, and it will do so more rapidly as it gets cheaper. And wind is advancing rapidly too.

And remember, the article is about fusion electricity not starting up for another 30 years. By then, as my original comment said, it will be mostly or all renewables, and so there will be no way to persuade countries to spend trillions on fusion.

Musk's comment were intended to demonstrate that powering the US on solar is practical - you don't need to cover the whole country in panels, you actually only need 10 square miles.

You wouldn't actually put all these panels in one place, because of transmission losses, putting all your eggs in one basket, etc...

The point being, that you can power the US with a reasonable, practical amount of panels.

You just need to cover the otherwise unused roofs to build what is essentially a distributed power generator. Maybe even use a 10 kWh battery for backup if it's cheap enough (under $1000) for each PV covered roof.

Yes. Tesla/SolarCity are doing exactly that - they're about 400,000 roofs in, so far.

Limiting those enterprising disruptors to those with 32 billion dollars to spare narrows the field a touch. :)

[1] http://innovativesolarfarms.com/solar-farm-cost-per-acre/ gives $500k per acre

That's a square a hundred miles on a side (10,000 square miles), not a square ten miles by ten miles (100 square miles).

Musk's point was that even a 10,000 square miles isn't all that big compared to the rest of the United States.