Rinnai Demand Duo 80-Gallon Hybrid Tankless+Tank Water Heater
Rinnai Demand Duo 80-Gallon Hybrid Tankless+Tank Water Heater Review
The Rinnai Demand Duo is a hybrid tank+tankless water heater combining an 80-gallon storage tank with a tankless heating element. Provides reservoir capacity for peak demand + continuous tankless flow for sustained use.
Specs: 80 gallons stored, 199K BTU integrated tankless burner, dual stainless heat exchanger, PVC condensing venting. Effective FHR exceeds 250 gallons (combination of stored + continuous heating).
The hybrid design eliminates the cold-water sandwich issue (tankless-only systems) while providing tankless's continuous output. Right answer for very large households or commercial-residential applications where parallel tankless install would be the alternative.
About $4,500 unit, $7,000-$9,000 installed depending on plumbing and venting work. Right buyer: very large household (6+ people) with substantial overlapping demand, or small commercial application (small restaurant, salon/spa).
- Natural gas combustion — faster recovery than electric resistance at comparable tank size
- UEF 0.96 — top-tier efficiency; qualifies for Inflation Reduction Act §25C residential credit
- 10-year warranty — solid above-average coverage for this class
- Large 80-gallon reserve — comfortably serves 5+ person households in peak-use periods
- 175-gallon first-hour rating — handles morning-rush simultaneous demand without shortfall
- Tank standby heat loss — tankless or heat-pump alternatives eliminate this continuous efficiency gap