The answer to 'tankless water heater vs tank water heater' is that tankless water heaters are generally more energy-efficient and take up less space, but they can have higher upfront costs. Tank water heaters are more affordable and familiar, but they use more energy and require more space.
Tankless water heaters heat water on demand, only using energy when you need hot water. This makes them up to 34% more energy-efficient than traditional tank heaters. They also take up much less space since there's no storage tank. However, tankless heaters have a higher initial cost, typically $1,000-$3,000 for the unit and installation. Tank water heaters are generally $400-$900 for the unit and installation.