Question: what is the best condensing tankless water heater?
Answer: Takagi T-H3-DV-N Condensing Natural Gas Tankless Water Heater. ...  Rinnai RUR98iN Ultra Series Heater. ...  Noritz NRC661-DV-NG Condensing Direct Tankless Hot Water Heater. ...  Naiven NPE-240-A Tankless Gas Water Heater. ...  Rheem RTGH-84XLP Condensing Propane Tankless Water Heater.