I am moving from an apt. which comes with paid hot water to my first house, which has 3 bathrooms. I live alone and am often away for a week to a month at a time, several times a year. I only need hot water for one shower a day, dishes a couple times a week and not at all for a lot of the year. Would it be better to have a tankless heater as opposed to a tank of water sitting unused, heated, wasting energy or is it better to drain out and shut off a conventional water heater when I'm going away?