The first thing to think about is what size water heater you will need. in size. Some are small enough to carry with you on a camping trip while some can be large enough to heat the water in large homes. So to be sure to buy the right water heater for your home, first you need to think about what is the maximum hot water you will have to use at once. Perhaps your home has multiple showers individuals will use at the same moment. Or maybe you live by yourself and will never be using hot water in more than 1 room at a time. Whatever your requirement may be there's a tankless water heater out there for you.