Best High-Flow Gas Tankless Water Heaters (2026)
Gas tankless water heaters whose official ENERGY STAR records list a maximum flow of at least 5.7 GPM, ranked on the same published-spec score as the main comparison.
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- 1CHighest published-spec match in this shortlist
Camplux RT199iB
Score is within our gas tankless water heaters ranking8.7/10UEF 0.98; maximum 5.8 GPM; minimum 0.6 GPM; connected-capable.
What we like
- Highest official uniform energy factor in this comparison (0.98)
- High official maximum flow (5.8 GPM)
- ENERGY STAR lists this model as connected-capable
Watch out for
- No additional scored gaps in the official record we used
- 2CClosely related alternative
Camplux RP199iB
Score is within our gas tankless water heaters ranking8.7/10UEF 0.98; maximum 5.8 GPM; minimum 0.6 GPM; connected-capable.
What we like
- Highest official uniform energy factor in this comparison (0.98)
- High official maximum flow (5.8 GPM)
- ENERGY STAR lists this model as connected-capable
Watch out for
- No additional scored gaps in the official record we used
- 3RAnother official-spec alternative
Rinnai CX199I
Score is within our gas tankless water heaters ranking8.1/10UEF 0.98; maximum 5.8 GPM; minimum 0.1 GPM.
What we like
- Highest official uniform energy factor in this comparison (0.98)
- High official maximum flow (5.8 GPM)
- Lowest official minimum activation flow in this comparison (0.1 GPM)
Watch out for
- ENERGY STAR does not list this model as connected-capable