It depends on where you live and your expectations how well a tankless works. They need to be bigger if your winter water temps are low, and bigger yet if multiple things will be running at once. Then, if you water quality isn't great, you need to clean out the mineral deposits from it (like a teapot), or it will get all crudded up. It requires a large gas supply, so yo umay need to upgrade your service and the flue pipe (SS), is expensive, and hopefully, you won't need much to vent it outside. If you search, you'll find all sorts of comments on tankless, most not so good, an occasional lover...as I said, it depends on your expectations and physical plant. The standby losses from a good tank-type aren't all that bad, but the heating efficiency of a tankless might be lower; depends on the model. Also note if you want a trickle of hot water, a tankless may not turn on (this would apply to warm as well as a trickle of hot). Increase th eflow just a little, and then poof, it's too hot.