How long is your machine on per day? How many cents do you pay per kilowatt-hour? Is your boiler insulated?
Those factors make a huge deal, and as has surely been suggested before, the laziest (albeit time-consuming) and most accurate way to check is to put your machine on a
Kill-A-Watt monitor.
I would guess, as I have the same machine as you (mine is insulated, though), that you're looking at saving maybe $5-15 per month max, probably on the low end of that. I need to look at my kill-a-watt to check how mine's been doing...