Yep not a lot at all. I've got one of those plug-in power monitors that displays the amount of power draw - my Dell 630m uses 35-40 Watts when it's up and running. My PC, comparatively (including display) is using 150 Watts right now, and that'd be nearer 180 or so if I had my proper graphics card in (Radeon 1800XT). Pop a game on and it goes up to 300W or more.
As for voltage, all I can really say is that my Dell's battery says it's rated for 11.1V.