I've got a heatloader that xsuperbgx made for me. It is not adjustable, and just plugs into the outlet (white cord in the background). I haven't read how much power it draws yet, as I can't find where my kill-a-watt went.
It is awesome for testing this stuff. I expected the testing to be difficult, but its harder than I expected - I don't think I would have been able to get results I was satisfied with if it weren't for this tester. I have had to redo a number of tests already, and I have a few more to redo yet... But if I was trying to do this on an actual rig I think it would be a real nightmare.