ScottH said:
No, playing by yourself does not change the house edge. Like CheffJJ said, you'll just be playing faster, so you'll be losing money faster as well.
Agreed, when playing at a table thats nearly full you might be getting in, 60 hands an hour, this is a generally accepted number that most pit crews will use in figuring out your comps.
Playing heads up you can be exposed to 200+ hands sometimes if your quick with decisions, and without counting, you're just exposing yourself to more of the houses edge, basically your exposing yourself to the houses edge, so you are more likely to lose since you are getting into more long run.
Now if this was a counter at the single table, he would be able to vary the bet into a positive count and while getting more cards in, will also reach that long run type advantage that counters have and will see more money, all of course in the long run.
Comps is another issue that I'll put in here too.. even if you only play head up against the dealer, the pit will still put you into that 60 hand an hour equation they use for figuring our comps, so if you are trying to rack up comps, this isnt the way to do it, but thats a completely different subject.