Rinnai RU199iN Tankless Water Heater vs Rinnai RX180iN Tankless Water Heater

Both are indoor condensing Rinnai tankless units with stainless heat exchangers, so build quality and parts support are close. The RU199iN wins on capacity: 199,000 BTU and roughly 11 GPM handles larger homes and simultaneous showers plus laundry. The RX180iN wins on efficiency, with a 0.98 UEF versus 0.93, and it ships smart-ready with Wi-Fi built in. Buy the RU199iN for a busy household with several bathrooms; buy the RX180iN for a smaller home where efficiency and app control matter more than peak output.

• Choose the RU199iN if you have a large home, multiple bathrooms, or high simultaneous hot water demand and want the most output Rinnai's residential line offers.
• Choose the RX180iN if your household demand is moderate and you want higher efficiency plus built-in smart controls without adding accessories.