Ah well, if you finance it with interest, then sure thats all dependant on the rate.
It's a bit harder to calculate exactly how much you'll be paying down since the utility can increase fairly often. My utlility recently announced a avg. $11/month increase in natural gas costs which they want effective April 2009. Part of the actual press release states that part of the increase is to give shareholders a better return! What pricks!
Over 20 yrs or so, you would need to adjust your break even date at least 20 times I'd guess, and all of them in your favor.