It's an embedded laptop graphics card, but if you're playing for a while it gets hot enough to burn unprotected skin. That's a sign that it's using quite a bit of electricity. The adapter's rated for 65W, and that'll run your electric bill up if you leave it on all the time. Plus, then double-hit because the air conditioner has to remove the heat.
Yeah, I'm watching my bills. Sue me.
As I said, I might try it, but by that point it's starting to seem a bit ridiculous.