TradesHow this works
The decision between a tank and a tankless comes down to whether a single tankless can keep up with your busiest moment. Heating water takes a fixed amount of energy per degree, so a tankless makes less hot water when your incoming water is cold. The tool takes your peak flow and your temperature rise, works out whether a typical single unit covers it, and if not, it points you to a tank.
Even when a tankless would keep up, a tank is often the cheaper and simpler choice. The tool shows both, with the tradeoffs, so the call is yours.
Common questions
Will a tankless keep up with my house?
It depends on two things: how much hot water you use at once, and how cold your incoming water is. A tankless makes less hot water when it has to heat colder water. Enter your peak flow and your incoming temperature and the tool tells you whether a single unit keeps up.
Why does cold incoming water matter so much?
A water heater raises the water by a fixed number of degrees per unit of energy. If your incoming water is 40 degrees and you want 120, that is an 80 degree lift. In a warm climate it might only be a 50 degree lift. The colder it starts, the less flow a tankless can deliver.
Is tankless always better?
No. Tankless gives endless hot water and saves space, but it costs more and often needs a bigger gas line and venting, or a heavy electrical upgrade. A tank is cheaper and simpler and is plenty for many homes. The right answer depends on your demand and your budget.
Sources: Heat-rise physics: BTU/hr = 500 x GPM x rise (exact) · Typical residential tankless and tank capacities (planning values). Engine version 1.0.0. Risk tier 2.