The Best Bosch Tankless Water Heaters

A review of Bosch tankless water heaters, including condensing and conventional on-demand gas models with a selection of the most advanced models to buy, quality features, specs, and benefits. Explore buying tips and top-selling models.

A German manufacturer Bosch and its perfectly engineered water heating systems give you a variety of high-quality tankless models with very simple tasks; to provide an instant (or almost instant) and endless supply of hot water for your home - for less.

And not only that, in these small and compact Bosch tankless products, there is a potential to save up to 50 % of energy when comparing to the tank-type heaters while producing enough hot water for multiple showers, bathtubs, kitchens, small or large houses. This is very important as water heating accounts for around 20% of energy usage in North American homes.

Bosch tankless water heaters - Buying tips

Bosch tankless water heaters are found in various types and sizes; condensing and non-condensing (conventional), small for single, and large for multiple applications. Some Bosch tankless products can be used in solar, recirculation, and space heating applications and mobile homes.

Top selling models

 Advantages and benefits

Great savings

Bosch tankless water heaters have a tank-less design allowing users to utilize hot water anytime, in endless supply, and only when the hot water is needed, eliminating the standby heat loss, resulting in high energy savings. For example, the best Bosch tankless water heater, Therm ES 1210, with its 98% energy efficiency, has only 2% in heat loss, while the tank type has over 20%.

As the Bosch condensing water heaters are designed with the pre-mix combustion process, this brings even more benefits to the users; higher energy factor for more savings, low NOx gas emission for better environmental protection, and lower exhaust temperature allowing cheaper venting pipes and flexible installation.

Quality heat exchangers

Every Bosch tankless water heater is equipped with a heat exchanger made of corrosion-resistant copper, while the condensing models also utilize a secondary one made of the combination aluminum/copper. The quality of the heat exchangers is significant due to the constant exposure to high thermal stress coming from the powerful gas burners.

High performance

The gas burner can modulate its power, so the heater consumes only the energy needed for heating, reducing the operating costs. The efficiency and performance of the water heaters are maintained high as the models come with the Scale Prevention system.

A dual-fan, modulating vertical gas burner, and built-in turbulators work together to reduce or prevent the scale buildup inside the narrow passages of the heat exchangers, therefore, preventing high thermal stress and premature failure.

A vertical, fully modulating gas burner ensures clean gas burning while the active bypass makes sure that there is less fluctuation in the outgoing water temperature, increasing the comfort when taking a shower, for example.

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Advanced electronics

The best water heaters from the Greentherm and Therm series come with a built-in electronic control board, so the LCD display and provided buttons are used to check, monitor, and control the temperature, program, and check the error codes using the advanced diagnostic system.

Best models to buy

Bosch 1210ESBosch 1210ES

The best models to buy from Bosch tankless product group are condensing models from the Therm and Greentherm series.

Bosch Therm ES 1210 is the most powerful unit from this manufacturer, used in residential and commercial applications. It comes with a gas burner that can produce a high 225,000 BTU and provide ultra-high efficiency of close to 98%, making it ASME rated and ultra-efficient.

The high hot water flow of 12.1 GPM makes it capable of delivering hot water to large homes with multiple applications (up to 4 bathrooms operating at the same time). Bosch Therm ES 1210 can be combined into the cascade system with up to 24 units for even larger applications where higher flow rates are required.

Therm ES 1210 is factory-built to heat water to 140 F, controlled by an electronic system like most tankless water heaters. If a higher temperature of hot water is needed in residential applications, buy Bosch Greentherm C 1050 to achieve temperatures of up to 184 F when using the high temp kit. This model has the same size as the above Therm ES 1210 but is designed with a maximum gas power of 199,000 BTU and energy efficiency of 96%, making it eligible for the Energy Star program and other incentives.

The small size of 18" x 31" x 11" and weight of 74 lbs combined with the flexible venting allows easy wall-mount installation almost anywhere inside the house, even outside when using the outdoor models.

Model selection

  • Bosch Therm C 1210 ES condensing - the most powerful and with the highest water flow rate
  • Bosch Greentherm C 1050 condensing - largest Energy Star model
  • Bosch Greentherm C 950 ES condensing
  • Bosch Therm C 940 ES non-condensing - highest capacity of non-condensing models
  • Bosch Therm C 830 ES non-condensing

Key benefits of the best models

  • On-demand water heating
  • An endless supply of hot water
  • High savings of 50% when comparing to tank-type
  • Small and compact for easy handling and wall installation
  • Versatile in using different fuel sources (natural and propane gas), multiple installation options, and the venting configuration
  • High efficient
  • Advanced electronics and diagnostics system
  • Modulating gas burner for an increased comfort
  • Opportunity to provide hot water as a single unit or combined with other models
  • Low greenhouse gas emission
  • Long warranty of 15 years
  • Average life expectancy of 20+ years


Due to the high-quality features and inside elements, Bosch tankless water heaters are protected with an extended 15-year warranty on the heat exchanger and 5 years on other parts. According to the manufacturer, the life expectancy is over 20 years.

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