Rinnai RL75iN Luxury Series Interior Tankless Water Heater

The Rinnai RL75iN is the indoor-rated non-condensing version of Rinnai's "Luxury" tankless series, sized at 180,000 BTU for medium-demand households. It is positioned below the flagship RU/RX condensing series at a meaningfully lower price point — typically $1,400 unit versus $1,800–$2,400 for the condensing models. The "iN" suffix means indoor mounting with stainless-steel B-vent venting; the "L" identifies it as the Luxury Series (Rinnai's value-positioned residential line).

Specs: 180,000 BTU natural gas input (also available as LP), UEF 0.82, 7.5 GPM at a 35°F rise or 3.7 GPM at a 70°F rise, copper heat exchanger. Compatible with the Rinnai Control-R app for remote temperature setting and fault-code monitoring. 12-year warranty on the heat exchanger, 5-year on parts.

The right buyer is a household that wants tankless capacity without the install premium that condensing units carry. The non-condensing exhaust temperature requires stainless steel B-vent (or Category III chimney liner) rather than the PVC venting used by condensing models. In retrofits where an existing atmospheric gas tank used a B-vent chimney, the RL75iN reuses much of that infrastructure — saving $500–$1,200 in venting work versus a condensing tankless retrofit. The tradeoff is the lower UEF (0.82 vs 0.96 for condensing), worth roughly $50/year in additional gas cost for a typical household.

Not the right fit for households without existing B-vent access (where PVC venting is required by the install location), or for households doing a major plumbing renovation where the condensing-unit install premium is being absorbed anyway. In both those scenarios, the condensing RU199iN at $1,800 is the better choice — same form factor, same Rinnai service network, materially better efficiency.