I just finished up a tankless hot water heater install this weekend. For once the timing worked out well and I was able to do the roof work on the last semi-warm day and then finished the plumbing just before we had a little freezing rain. Good points: I gained a nice little closet to store some tools and pool supplies. The wife is ecstatic never worrying about running out of water. The temperature is always consistent vs. tempered in a tank heater. We are on natural gas so I don't expect a world of savings, but it's nice to use zero when we are away for three weeks. Bad points: Cost will never pay back unless natural gas prices go crazy. The heater and venting was $1100, misc. piping $400, and another $30 in hardware. Nothing from your old heater is reuseable, this isn't a rip and replace by any means. In my case it also took about 15 hours of labor vs. about an hour for a normal heater. This is one of two, I will definetly replace the other tank heater with a tankless when the time comes. Anyway I thought it might be interesting to discuss in case anyone is considering it. Here is a picture just after startup, still have to insulate and button everything up.