Here's a thought relating to buying not renting. Back when I bought my 60gal tank the rental I saved equalled my upfront cost in just five years; after that it was free. The rental I had Hydro take away when I bought the house was 20yrs old. The previous owners coulda bought four tanks for what they'd paid in rent. How long do you intend to pay rental on that tank, and what are you getting for the money you're giving the utility every month?
As for the tankless vs. paying to keep a whole tank of water piping hot and instantly ready for showers, dishes and laundry all day when everyone's at work or school, and all night when everybody's tucked up in bed, look at your use patterns. Most of the time you turn the hot tap, isn't it just for a hand or face wash? And down in the basement a whole 40-60 gallon heater's cycling on and off a coupla times an hour to give you that bit of warm water. You're giving the utility money to heat all that water you're not using 24x365.
That tankless heater will give you the only useful output either system gives—hot water when you want to use it. But you won't be paying uselessly for waste.
You do the numbers, but given that energy prices are going up, as more and more folks compete for ever more expensive sources, I'd look at what places where energy has always cost more than here. There's a reason those tankless jobs are European imports. Makes them expensive, but not stupid.
Your question really should'nt have been: Why do I go tankless? It shoulda been: When?
