In case it isn't obvious 500 TWh/year is less than 80 GW.
More clarity: 500 TWh/yr is ~57 GW on average. From a quick google, it seems that peak electricity usage is 60-80 GW, which makes the 80 GW milestone much more interesting.
With some caveats perhaps... theoretically speaking if 80GW of PV were to produce at 100% output power 24/day that would be about 700TWh in a year