Rinnai’s Demand Duo commercial hybrid water-heating system delivers hot water performance that meets peak demand. Combining the on-demand continuous supply technology of tankless with an energy-efficient 119-gal. storage tank, it is a solution for direct replacement of most traditional 100/199 commercial standard and high-efficiency tanks, Rinnai notes. It features multiple venting options; a first-hour rating of 315 gal. with recovery of 231 gal. (at 100° F) and an integrated temperature controller.