I've seen previous mentions of it (probably on /r/microsoft or somesuch), though they stated 3h in "tablet mode" (screen only, not design mode with the screen reverted on the base)

edit: https://www.reddit.com/r/apple/comments/3npv7p/microsoft_sur...? has multiple mentions of the 3h "screen only" version ([e.g.](https://www.reddit.com/r/apple/comments/3npv7p/microsoft_sur...), I'm guessing it was made explicit during the unveiling or just after.

I wonder if the top will recharge from the base if I have been using it in tablet mode for a while, then put it back in laptop mode without plugging into external power?

It certainly explains how it isn't super top heavy.

It's true, except for the part that it gets four hours. It should be more like 2-3h.