Best Bosch Hot Water Heaters
Review & Buying Tips
(updated 2018)

So, what are the best Bosch hot water heaters for your residential water heating needs? Let's review the most efficient and high performing tankless and condensing water heaters, from the Therm and Greentherm series.

What to look for when searching for the best water heater

To find out which are the best tankless water heaters from Bosch, we have reviewed every single gas unit the Bosch manufacturer has to offer. We used the following criteria and directions for choosing the best Bosch models:

  • What are the most advanced and useful features, the best Bosch tankless water heaters have to offer?
  • The best models are the those that provide savings on gas, use green technology and help in reducing the emission of greenhouse gases.
  • Do the units provide an innovative design?
  • What are the specifications?
  • The best Bosch hot water heaters have to provide flexibility in installation.
  • The water heaters have to be versatile to work in different applications, such as recirculation, space heating...

Once the best Bosch hot water heaters are chosen, we will do the detailed review; see what they have to offer, what are your benefits there, how much money do they cost and show the summary of what other users are saying.

We will also review Bosch heater's specification for every single gas tankless water heater, does it provide enough hot water for a family of 4, and can it support hot tubs and multiple applications.

Greentherm 9000

Greentherm 9000 series is recommended for the homeowners when replacing the traditional hot water tank. It offers the top water connections and integrated drain ports which allows easier installation.

No matter do you have a small or large home, there are seven models to choose from, which ensures plenty of hot water for your needs. Even for commercial applications.

The 9000 series of tankless water heaters are built as the indoor and outdoor models where the indoor include flexible venting for easy and fast installation.

While most of the models are built to use natural gas, with the conversion kit, the units can be converted easily to use propane instead.

The 9900 series comes in three models, having the power ranging from 160,000 to 199,000 BTU, and capable of reaching up to 8.7 GPM and energy factor of 0.99. They all utilize the recirculation pump to use if hot water is needed fast at some fixtures.

The 9800 series consists of four models having the same power as the above 9900 series, but the built-in recirculation pump is not available. The Wi-Fi is optional here.

The best one to choose is coming from the premium Greentherm 9900i SE model that utilizes the glass front and integrated Wi-Fi control so it can be controlled using the smartphone (through the app).

Features highlights

  • Seven models available
  • Energy Star approved
  • Energy efficiency up to 0.99
  • Water flow rate from 7-8.7 GPM
  • Top water connections (indoor models)
  • Built-in recirculation pump (some models)
  • The concealed built-in controller on outdoor models of 9800 series
  • Indoor and outdoor installation
  • Can be used with solar energy systems

Bosch Therm C 1210 ES review

Bosch Therm C1210 ES is the gas condensing tankless water heater, which comes with the highest efficiency and performance of all models from Therm and Greentherm series.

The condensing technology is what makes this Bosch hot water heater unique as it increases its efficiency and lowers the emission of greenhouse gases.


  • ASME certified - complies with the relevant standards and specifications.
  • Ultra-efficient water heating with over 98% efficiency.
  • High water flow rate of 12.1 GPM.
  • Up to 24 units can be linked into one system for high demanding homes or commercial applications.
  • Flexible direct vent installation; vent pipe can run horizontally or vertically by using the vent system with the concentric or two separate pipes.
  • The cheaper vent pipe is used (such as PVC or CPVC), as the water heater releases gases with the lower exhaust temperature. Maximum vent run is up to 63’.
  • Suitable for heating potable water and living space, also recirculation and solar.
  • Great warranty of 15 years.


  • High initial costs that include the prices and installation.
  • It is not Energy Star ranked (the only model with up to 199,900 BTU are taken into consideration).

Features and Specs

  • LCD display with the power bar, temperature, error code, flame, solar mode, and remote control indicators.
  • Program button (to adjust the temperature, fan speed and more).
  • The diagnostic system with the error codes for easy troubleshooting and fixing. The diagnostic menu also shows the fan speed, temperature, power, water flow, and other important parameters.
  • 225,000 BTU gas input.
  • 12.1 gallons per minute water flow rate.
  • Low minimum water flow needed for activation - 0.5 GPM.

One is for sure: the best Bosch hot water heater is usually the most expensive, which also uses the latest technology, materials, and the most advanced features.

Our recommendations; based on the experience in water heating, is to go with one that meets the demand, provides flexible installation and offers modulation for steady work and reduced temperature fluctuation... everything else is extra. If you are budget oriented, buy a Therm 520 HN; if looking for more gadgets, any Energy Star model is good enough.

For those who prefer the top of the line water heater, which utilizes the condensing technology, heats the water with the ultra high efficiency and low heat loss, is green or environmentally-friendly, the above Bosch C1210 ES as the best Bosch hot water heater is a perfect choice.

› Best Bosch hot water heaters

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