Bosch Therm 940 ES Review

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An overview of the Bosch Therm 940 ES, the largest non-condensing tankless water heater from Bosch, a great unit for 4-bath homes.

Features and specifications

Bosch 940 ES is the standard type tankless water heater that is designed as the direct vent unit with the gas sealed combustion chamber for safe use inside the house. With the right venting kit, it can be installed outdoors too.

It’s powerful and Low NOx burner and one long-lasting copper heat exchanger generate lots of power that results in high energy factor of 0.83, making it Energy Star compliant. Bosch 940 ES is the whole-house water heater where its maximum water flow rate of 9.4 gallons per minute makes it ideal for larger families as up to four simultaneous showers can be used. Also, the minimum water flow of 3 gallons makes the usage also convenient where a smaller amount of hot water is needed.
Bosch Therm 940 ES model is approved for the domestic hot water recirculation applications so you can get hot water faster than if the circulation pump is not used.

This tankless model can also be paired with the storage tank and Ariston mini-tank Tronic, where more hot water is needed, while the wait time is reduced. For larger homes and high-demanding applications one tankless unit might not be enough, so the recommendation is to use the Intelligent Cascading Kit so up to 24 units can be connected into one system to generate more hot water.

Bosch Therm 940 ES

The water heater can also be combined with the solar water heater system if the solar panels cannot provide enough hot water, the gas tankless acts as the booster.

The advanced electronics allow gas and water valve modulation, so the power, based on the water needs, adjusts automatically from 19,900 to 199,000 BTU. Another great advantage is the real-time diagnostic represented by the failure codes on the LCD display, which makes the problem diagnostic and repair easy.

As seen from the above technical data and when compared to other non-condensing models, Bosch Therm 940 ES is the most powerful non-condensing tankless water heater that produces the highest water flow of all conventional tankless water heaters from Bosch. Due to the innovative design, the water heater can run on natural or liquid propane gas, while its small and compact design ensures flexible installation and wall mounted inside or outside the residential house, commercial office, even the mobile homes.


Bosch provides a long warranty of 15 years on the heat exchanger and 5 on other parts.

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Pictures - courtesy of Bosch company

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