We get 127 million km² worth of direct sunlight at any given time. At the highest efficiency, we can get some 200 W of electricity from each m² of that. That's some 25 million GW. We'll only run out of sunlight in 70000 years at this rate of growth!

Yes, the post is probably about GWp, in which case you should more than double that if using solar-tracking panels or quadruple that for static panels.