Reddit is apparently the 3rd most popular website: https://old.reddit.com/r/technology/comments/8n959q/reddit_j...
No idea where this info comes from but it gives 1.8 TWh/yr for (the now fourth most popular site) facebook in 2016: https://www.statista.com/statistics/580087/energy-use-of-fac...
Does it make sense for total reddit usage to be ~3.5 TWh/year in 2018? It seems to be in the right ballpark, but who knows how circular these calculations are.