Both are good solutions for your home water system and both have their advantages and disadvantages. Hot water tanks will typically use more energy to heat and maintain the temperature of the water in the tank, while tankless systems (also known as on-demand systems) heat the water when you need it, so you only heat what you use which can save you energy. Tankless systems supply as much hot water as you need, while the tank capacity of a hot water tank limits the amount of hot water available at a given time. Hot water tanks are generally more affordable to purchase and install, and tankless hot water systems are more expensive to purchase and typically more expensive to maintain over time.