Best High-UEF Gas Tankless Water Heaters (2026)
Gas tankless water heaters whose official ENERGY STAR records list a uniform energy factor of 0.98, ranked on the same published-spec score as the main comparison.
Affiliate disclosure: We earn a commission if you buy through links on this page, at no extra cost to you. It never affects our rankings, which come from the published scoring formula. As an Amazon Associate I earn from qualifying purchases. Learn more.
- 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