Bosch Condensing Water Heaters
Review and Buying Tips
(updated 2017)

Discover the new Bosch condensing water heaters for residential tankless water heating. Find out the most advanced features, including the advantages and benefits of the
Therm C 1210 ES and Greentherm C 1050 ES models.

Condensing models review

Bosch US offers two types of condensing water heaters for potable and residential use: Therm C 1210 ES and Greentherm C 1050 ES, both models designed to heat water by using the natural and propane gas. Condensing models are the most advanced type of tankless heaters in a wide array of Bosch products, including the discontinued Aquastar models.

With the low NOx burner and ultra-efficient combustion, Bosch condensing water heaters are capable to reduce the greenhouse gases significantly and comply with strict regulations. Two condensing heaters can be combined into one system by using the Intelligent Cascading feature, also with other systems such as the solar thermal, recirculating, hydronic radiant floor and space heating.

Review of Bosch Therm C1210 ES

Bosch Therm C1210 ES tankless water heaterBosch Therm C1210 ES

Bosch condensing water heaters from C1210 ES series are the most powerful models and with the highest water flow of all residential condensing and non-condensing models from this manufacturer.

This particular model was designed so it can compete with the most advanced models from Rinnai, Noritz, and other tankless brands.

It is used for residential water heating, and with the maximum gas input of 225,000 BTU, it is can provide high thermal efficiency of 98% and high 12.1 gallons of hot water.

This is what makes these advanced water heaters ideal for large homes with high hot water demand (up to five showers during the summer or up to three in winter time).

Modulating gas valve and an electronic computer board will work together so the unit can lower its power to approximately 25,000 Btu, which is great for smaller jobs, such as hand and face washing or shaving.

The water heater is highly efficient, but not Energy Star rated, as it has the gas input, which exceeds the maximum considered, and therefore, the manufacturer is not obliged to show the energy factor value.

Review of Bosch C1050 ES

Bosch C 1050 ES tankless water heater with condensing technologyBosch C 1050 ES

Bosch C 1050 ES is, by its design and technology almost the same unit as the C 1210 ES, but it is smaller with less power. The maximum gas input is 199,000 Btu, and the energy efficiency is 92%.

It is smaller than the above unit, but it still produces a high hot water flow, which is 10.5 gallons, more than the largest non-condensing unit. Bosch Therm C 1050 ES is used for homes with up to five fixtures (in summer) or three (in winter) working simultaneously.

The highest energy factor on non-condensing water heaters is 83% so when it compares to the above models; you will see that condensing models are at least 10% more efficient.

Advantages and benefits

Flexible venting

Both Bosch condensing and tankless water heaters come with the small and compact design, which makes them fit almost anywhere, also installed either outdoor or indoor. Indoor type is the most common type where the water heater uses the PVC, CPVC and ABS vents for the exhaust. This type of vents is cheaper than stainless steel used in non-condensing, and the installation is faster and easier.

Condensing technology is what allows the use of vents made of these materials as the temperature of the flue gases is lower than in non-condensing models. Built as the direct vent models, the water heaters can use long 63-feet vent pipes. The vents can be installed vertically or horizontally and with the concentric or twin-pipe option, which all together gives them great flexibility during the installation.

Advanced features for high performance

Modulating vertical burner design with a constant gas/air ratio control, dual-fan and specially designed heat exchangers help the water heaters last longer, as they reduce high thermal stress and provide optimal combustion. There are two heat exchangers, the primary, made of copper and the secondary made of the lightweight and corrosion-resistant aluminum.

Built-in turbulators help in reduced scale build-up for the increased performance, maximum efficiency, and long-lasting water heating.


Therm control panelTherm control panel

Moreover, for precise temperature control and easier problem solving, each model is equipped with the diagnostic system.

At the front of the units, there is a control panel with the LCD display which shows the failure codes, status, and temperatures, including program, reset and On/Off buttons.


All Bosch condensing water heaters are equipped with the several safety features:

  • Freeze protection down to 5 F.
  • Minimum water flow for activation - 0.5 GPM.
  • Flame rod sensor for flame failure.
  • Temperature limit switch for overheating.
  • Inlet and outlet temperature sensors.
  • Back-flow temperature sensor.
  • Exhaust gas temperature sensor.
  • Condensate drain.

Bosch condensing water heaters come with the warranty of 15 years on the heat exchangers, and 5 on other parts, while other manufacturers usually provide 10 years. You can rely on these products since the Bosch manufacturer has been dealing with condensing products for over 25 years.

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