Bosch Tronic US9-2R Pro Under-Sink Electric Tankless Dis

The Bosch Tronic 3000 US9-2R is a 9-kilowatt point-of-use under-sink electric tankless water heater designed to deliver instantaneous on-demand hot water at one to two fixtures without a storage tank. It is intended for installation directly under or adjacent to the sink it serves, eliminating the wait for hot water caused by long supply runs from a distant primary water heater. The US9-2R heats only the water being drawn at the moment of use, with no standby heat loss from maintaining a stored volume of water at temperature.

The US9-2R requires a dedicated 240-volt, 40-amp hardwired electrical circuit. It does not plug into a standard household outlet and must be connected by a licensed electrician using a hardwired installation at the location where the unit will be mounted. The dedicated circuit must be free of other loads and sized and protected in accordance with applicable local electrical codes. Customers should confirm the availability of a 240-volt circuit at the installation location before ordering.

Self-modulating technology in the US9-2R automatically adjusts the output of the electric heating element in real time based on the incoming cold water temperature and the current flow rate being drawn. When incoming water is warmer — such as during summer months — the element uses less power to reach the desired output temperature. When incoming water is colder, the element increases output to compensate. This continuous adjustment ensures efficient energy use across varying seasonal conditions and flow demands without requiring manual adjustment.

The US9-2R can serve one to two fixtures simultaneously depending on the incoming cold water temperature and the combined flow rate of the fixtures being used at the same time. In warmer climates or during warmer months when incoming water temperatures are higher, two-fixture simultaneous service is more readily achievable. In colder climates or during winter months when incoming water temperatures are lower, single-fixture service at the full desired output temperature is the more reliable operating expectation. Customers with high simultaneous demand requirements should confirm the US9-2R's output capacity is appropriate for their specific climate and usage pattern before purchasing.

RuralEnergy.com carries four models in the Bosch Tronic 3000 2R under-sink electric tankless series: the US3-2R (part number 7736505867), the US4-2R (part number 7736505868), the US7-2R (part number 7736505870), and the US9-2R (part number 7736505871). Each model shares the same self-modulating under-sink tankless platform with the kilowatt output increasing across the lineup. The US9-2R is the highest-kilowatt model in the series and is best suited for installations requiring greater output capacity or the ability to serve two fixtures simultaneously.

The Bosch Tronic 3000 US9-2R does not include a pressure relief valve. A pressure relief valve must be sourced and installed separately as part of the installation. Local plumbing codes typically require a pressure relief valve on all water heating equipment regardless of whether the unit is a tankless or storage type, and the installer or licensed plumber completing the installation is responsible for selecting and fitting the appropriate valve for the application and jurisdiction.