A tank offers stored volume and simpler replacement in many existing layouts, but standby loss and floor-space needs remain part of the tradeoff.
An equipment efficiency claim is not an installed-cost quote. Upgraded gas piping, electrical capacity, venting, condensate drainage, water treatment, recirculation, or new penetrations can dominate the project decision.
Keep this boundary: The guide cannot select a heater without household demand and site measurements. Price and savings claims must come from the actual model and installed scope.