An often ignored consideration is that in Calgary we average ~11 degrees C difference between the heated inside temperature and the unheated outside temperature*.
This means that in all but 2-3 of months of the year, the heat loss from having a less efficient hot water vs. on-demand tank is "lost" into the house. This heat "loss" mostly displaces heating that your furnace would otherwise have to do.
On-demand water heating makes a ton of sense if you're in a hot climate where cooling is a significant concern, but it makes very little difference in Calgary. If you like how it works or the fact that you have unlimited hot water or more space in your furnace room, that's cool, but the economics made no sense at all for my household when we had the basement apart after the Bow River flood a few years back.
* ~4000 heating degree days per year / 365 days (
http://calgary.weatherstats.ca/metrics/hdd.html)