Yes, it can. Plasma 4 wasn't really suitable for it, but Plasma 5 is OK. Can't say much about battery life - it can differ a lot depending on the laptop and how well various power features of the chipset are documented. A lot of time Intel for example are pretty sloppy and don't document things like that, so there isn't much Linux developers can do.

mjg59 wrote a number of comments on this subject.