I have one of the table top halogen ovens and when i bought it im sure they quote "up to 30% reduction in running cost, depending on current oven" so not an exact figure but should give you a rough guide ;-)
Hi, yes as lardhelmet said its an hour max unfortunately ;-( i have had mine a while now so they may of come up with a digital control panel that goes higher by now, might be worth a google. I love my halogen, would not be without it now :-)