Bosch Greentherm 9000 9.9 GPM Tankless Water Heater

The Bosch Greentherm 9000 9.9 GPM Tankless Water Heater (WTG-9000-NG) is Bosch's premium condensing tankless for the US market. 9.9 GPM peak flow, 199,000 BTU condensing burner, 0.95 UEF, 15-year heat exchanger warranty. Bosch's European engineering heritage shows in the build quality and modulation range, but US market share trails Rinnai and Navien — verify installer availability in your area.

Headline specifications

• Type: indoor condensing tankless, natural gas (LP-convertible)
• Maximum flow rate: 9.9 GPM at 35°F rise
• BTU input: 17,000–199,000 BTU/h (modulating)
• Energy Factor (UEF): 0.95
• Min activation flow: 0.5 GPM
• Temperature range: 100°F – 140°F
• Modulation: 12:1 turndown
• Warranty: 15-year heat exchanger, 5-year parts
• Venting: PVC/CPVC up to 100 ft
• Dimensions: 28" H × 17" W × 11" D

Who this model is for

4–5 person households with 2 bathrooms, peak demand of 2 simultaneous demand points, existing natural gas service with 3/4" gas line. Buyers who specifically want Bosch's European engineering build quality. Homes in regions where Bosch has a service-network presence (parts of the Northeast, parts of West Coast, urban metros with European appliance dealerships).

For buyers in regions where Bosch installer presence is thin, the parallel-spec Rinnai (RU199iN) or Navien (NPE-240A2) is the safer pick — better service-network depth, easier parts access.

Where the Greentherm 9000 beats the alternatives

Vs Rinnai RU199iN ($1,645): Bosch 9.9 GPM vs Rinnai 11.1 GPM. Same warranty class (15-year). Same UEF (0.95 vs 0.96 — wash). Rinnai wins on flow and US installer network depth. Bosch wins on build-quality reputation if you have access to a Bosch dealer.

Vs Navien NPE-240A2 ($1,499): Navien 11.2 GPM, ComfortFlow buffer included, NaviLink WiFi built in. Bosch 9.9 GPM, no buffer, no built-in WiFi. Navien clearly better-equipped at lower price. Choose Bosch only if Bosch has specific installer-relationship advantage in your area.

Vs Bosch Greentherm 5300 ($1,249): 9000 ~$400 more for 9.9 vs 5.3 GPM and the larger 199K BTU burner. Step up to 9000 for 4+ person households; 5300 is correct for 2–3 person.

Where it falls short

Bosch US service network is real but smaller than Rinnai/Navien. Replacement parts may have longer lead times. Local installer expertise varies — strong in metros with European-appliance dealer presence, sparse elsewhere.

No built-in WiFi or smart-home integration. Rinnai Sensei, Navien NaviLink, and Rheem EcoNet all ship app integration standard at the same tier.

Cold-water sandwich without buffer tank. Navien's ComfortFlow is the obvious comparison.

9.9 GPM is competitive but trails Rinnai 11.1 and Navien 11.2 at the flagship tier.

3/4" gas line, PVC venting, annual descaling — same constraints as all condensing tankless.

Install considerations

Verify 3/4" gas line capacity to 199,000 BTU. PVC/CPVC schedule 40 vent up to 100 ft. 120V outlet near install. Service valves needed for descaling. Verify local Bosch-certified installer availability before committing.

Install cost: $1,200–$2,200 like-for-like; $2,900–$4,800 tank-to-tankless conversion.

Maintenance

• Annual descaling required to maintain warranty
• Inlet filter clean annually
• Burner inspection every 3 years by Bosch-certified technician

Bottom line

The Bosch Greentherm 9000 is the Bosch flagship condensing tankless — 9.9 GPM, 0.95 UEF, 15-year warranty. Spec-competitive with Rinnai and Navien flagships but trails on installer network and feature integration (no built-in WiFi, no buffer tank). Right pick if you have specific Bosch dealer access or value Bosch's European engineering heritage. For most US buyers, the Rinnai RU199iN or Navien NPE-240A2 are safer defaults.