Tesla CEO Elon Musk — whose company makes electric cars and has a new solar roof panel division — told more than 30 state governors at the National Governors Association meeting in July exactly how much land is needed to power the entire country on solar energy.

“If you wanted to power the entire United States with solar panels, it would take a fairly small corner of Nevada or Texas or Utah; you only need about 100 miles by 100 miles of solar panels to power the entire United States,” Musk said at at the event in Rhode Island. “The batteries you need to store the energy, so you have 24/7 power, is 1 mile by 1 mile. One square-mile.”

It’s “a little square on the U.S. map, and then there’s a little pixel inside there, and that’s the size of the battery park that you need to support that. Real tiny.”

Musk laid out his vision for renewable energy that relies on storing power from the sun via solar panels — Musk would probably prefer the solar panels are made by Tesla — to fill the enormous demand for energy in the areas of transportation, electricity, and heating.

Currently, about 10 percent of energy in the U.S. is renewable.

Solar roof panels in Los Angeles. Flickr / Clownfish

1. Combine Rooftop Solar Panels and Utility-Sized Solar Plants

Musk sees the solar future for America as a combination of rooftop solar — the panels on a house in the suburbs — and utility-scale solar that can make up needs in other areas. Recently, Tesla confirmed it would build a massive solar-powered battery to help power-starved South Australia.

The Tesla Powerpack setup is seen in this company rendering. Tesla Powerpack

Musk would likely want to see the Tesla Powerpack — its utility-scale product that uses fields of solar panels and dozens of car-sized batteries — used.

2. Use Other Power Sources During the Transition

“We’ll need to be a combination of utility-scale solar and rooftop solar, combined with wind, geothermal, hydro, probably some nuclear for a while, in order to transition to a sustainable situation,” Musk explained on Saturday.

3. Build Infrastructure and Localize Power

Localized power — aka solar panels on a roof — is important because it reduces infrastructure, like big power lines.

“People do not like transmission lines going through their neighborhood. They really don’t like that, and I agree,” Musk said.

“Rooftop solar, utility solar; that’s really going to be a solution from the physics standpoint,” he said. “I can really see another way to really do it.”

Why solar energy over other methods of power generation? Musk says humans have been relying on the sun for as long as there have been humans, basically. It’s worked up to now.

The sun powers all this anyway. Unsplash / Tony Reid

“The Earth is almost entirely solar-powered today, in the sense that the sun is the only thing that keeps us from being at the temperature of cosmic background radiation, which is 3 degrees above absolute-zero,” he said. “If it wasn’t for the sun, we’d be a frozen, dark ice ball. The amount of energy that reaches us from the sun is tremendous. It’s the 99 percent-plus of all energy that Earth has.”

After all, the sun’s a mind-bogglingly big energy ball, anyway: “People talk about fusion and all that, but the sun is a giant fusion reactor in the sky. It’s really reliable. It comes up every day. If it doesn’t, we’ve got bigger problems.”

Going on Solar Means Going Off Fossil Fuels

South Dakota Governor Dennis Daugaard asked why exactly Musk thinks electric cars have a future in the face of very low gasoline prices. (Musk envisions Tesla’s vehicles running off power captured by solar panels that recharge a car’s battery. It all goes back to the sun for him.)

After saying “there’s no question whatsoever that all transport — with the ironic exception of rockets — will go fully electric,” Musk explained the “big challenge” for electric cars competing with gasoline-powered vehicles: Essentially, it boils down to the fact that pollution from gasoline-powered vehicles has a huge impact on literally everything, except, crucially, the price of gas.

“There’s an unpriced externality in the cost of fossil fuels,” Musk said. “The unpriced externality is the probability-weighted harm of changing the chemical constituency of the atmosphere and oceans. Since it is not captured in the price of gasoline, it does not drive the right behavior. It’d be like if tossing out garbage was just free, and there was no penalty, and you could do it as much as you want. The streets would be full of garbage. We’ve regulated a lot of other things, like sulfur emissions and nitrous oxide emissions; it’s done a lot of good on that front.”

A gas and oil refinery in Bismarck, North Dakota. Getty Images / Andrew Burton

Surprisingly, Musk said he does feel some pity for big oil, in that when those companies were founded more than 100 years ago, there was very little indication that their logos would be seen as villainous a few generations later.

“They worked really hard to create those companies,” Musk said. “They feel like they are being attacked on moral grounds. And it is true that we cannot instantaneously change to a sustainable situation.”

He added one caveat, though: “But then those guys will also fight pretty hard to slow down the change, and that’s really what I think is morally wrong.”

Watch the full keynote below. The exchange begins at the 1:03:55 mark.