I've been studying how quickly we can get energy out to the poor countries - a lot of which are in Africa - and how little progress we've made there. There's no more electricity today in sub-Saharan Africa per person than there was 20 years ago.

Intermittency [in availability for wind and solar] changes the economics, particularly this requirement that the power company at all times be able to require power. That's large.

Vision without execution is daydreaming.

It's pretty incredible to look back 30 years to when Microsoft was starting and realize how work has been transformed. We're finally getting close to what I call the digital workstyle.

In 80% of the world, energy will be bought where it is economic. You have to help the rest of the world get energy at a reasonable price.

(On being the world's richest man) I wish I wasn't ... There's nothing good that comes out of that. You get more visibility as a result of it.

I went public too soon. Stay private as long as you can.