AO Smith ProLine Tankless 6.5 GPM Gas Water Heater
AO Smith ProLine Tankless 6.5 GPM Gas Water Heater Review
The AO Smith ProLine Tankless is a 6.5 GPM natural gas tankless water heater positioned in AO Smith's mid-range residential tankless lineup. 180,000 BTU non-condensing, UEF 0.82. Right answer for 2-bath warm-climate homes or 1-bath cold-climate homes where the larger condensing units (Vertex Power-Direct Vent or Cyclone tankless) are oversized.
Specs: 180,000 BTU input, UEF 0.82, 6.5 GPM peak at a 35°F rise, copper heat exchanger with stainless secondary. Category III stainless B-vent venting (compatible with reusing an existing chimney from an atmospheric tank). Built-in recirculation logic when paired with an external recirc loop. 12-year warranty on the heat exchanger.
The ProLine Tankless competes directly with the Rinnai RL180iN and Rheem RTG-90DVLN-N at similar BTU classes and price points. Distinguishing features: AO Smith's stronger Lowe's-channel presence and dealer service network. About $1,300 unit, $2,800 installed including venting work.
Right buyer: AO Smith preference, 2-bath home in moderate climate, existing chimney that can serve as the B-vent path. Wrong buyer: 3+ bath homes (push to 199K BTU class instead), cold-climate homes needing winter overlap demand, or installations where chimney access is unavailable (PVC condensing venting on a Vertex tankless variant is the better match).
- On-demand operation at 6.5 GPM — no standby heat loss; unlimited hot water if demand is within flow-rate capacity
- 10-year warranty — solid above-average coverage for this class
- Requires dedicated 140K BTU gas supply line — undersized gas piping is the leading cause of flow-rate shortfalls