Bosch Tankless Hot Water Heaters
Review and Buying Tips

Explore the advantages and top features of Bosch tankless hot water heaters, including the most innovative models and top sellers.

An expert review of gas and electric Bosch water heaters, including popular series; Therm, Greentherm from gas, and Tronic from the electric group, all designed for efficient on-demand heating of potable water in residential and light commercial applications.

As water heating is the second-largest energy user in ahousehold, buying an energy-efficient, or even better – Energy Star unit is a wise choice for many homeowners. And this is where purchasing a Bosch tankless comes in place.

Bosch tankless provides endless hot water on demand, reduced energy consumption and savings on heating cost up to 50%, space-saving, and reduced energy consumption and gas emissions. Also, buying the condensing unit, with an efficiency of over 90%, savings are even higher.


Best sellers

Features to look for

Both Therm and Greentherm group of gas tankless water heaters come with a built-in digital control panel that monitors the temperature rise and programming with precise temperature adjustment and safety control. Models from the Greentherm 9000 series are even more hi-tech as they utilize Wi-Fi connection for increased control.

Also, thanks to the dual fan, modulating vertical burner, and built-in turbulators, the units can operate more efficiently and last longer, as the scale build-up would get reduced.

For homes with high hot water demand, or commercial applications, up to 24 models (some models), either Therm or Greentherm can be linked together in cascades. For those who prefer instant hot water delivery, heaters that utilize the recirculation pumps could be worth considering, as they make recirculation easy. A good example is Greentherm 9000. 

All the models are compact, lightweight, and wall-mounted, making them easy to handle and install and save the floor space for other use.

Bosch gas tankless

Bosch Therm series review

Bosch C 1210 ES tankless water heaterBosch C 1210 ES

Bosch Therm series is the newer line of the advanced condensing and non-condensing tankless water heaters that come with an energy factor that can reach a high 98% and a minimal amount of heat loss (around 2%).

Our focus will be on water heaters for residential use. Most of the models are non-condensing that come with the power range from 74,900 to 199,000 BTU and efficiency up to 83%. Also, there are three models with condensing technology and power ranging from 175,000 to 225,000 BTU and ultra-high thermal efficiency up to 98%. Some of the models are reviewed, and the links are shown in the list below.

Therm condensing models with low NOx gas emissions are environment-friendly, and due to the high efficiency, they are Energy Star compliant. In residential applications, they can heat water up to 140 F, while in commercial, up to 184 F, making it ideal for restaurants and hospitals. The smallest models, such as the 330 and 520 series, have a simple design; they utilize the piezo ignition and high-to-low temperature option.

Here is the list of the available models, ranked from the low and mid-efficiency to the most advanced with high energy factors.

The Bosch C 1210 ES, which is reviewed here in detail, is the largest and most advanced model that can deliver more hot water to demanding applications due to its flexibility to work in the Cascade setup and with other model types (solar and electric).

Bosch Greentherm series review

Bosch Greentherm tankless and condensing gas water heaters operate with an ultra-high thermal efficiency of over 94% and utilize several innovative features such as a modulating gas valve, active bypass, and intelligent electronics for maximum performance, temperature stability, and reliable operation.

All the models, either installed indoor or outdoor, have low NOx gas emissions and are Energy Star compliant, resulting in flexible installation, reduced pollution, and fantastic energy savings.

Due to the lower temperature of exhaust gases, Greentherm models can use affordable and easy-to-install PVC or PP vents using the concentric setup.

Greentherm models are available in two sizes only:

  • Greentherm C 950 ES
  • Greentherm C 1050 ES
  • Greentherm 9000

The smaller Greentherm C 950 ES comes with up to 175,000 BTU and water flow of 9.2 GPM (35 F rise) and larger Greentherm C 1050 ES with the power of up to 199,000 BTU and flow rate of 10.5 GPM (35 F rise).

The Greentherm 9000 series is the latest group of tankless and condensing water heaters from Bosch. There are seven models in this group, all with a high energy factor of up to 0.96. They come with the “industry leading” turn down ratio of 22:1, heating water from the lowest gas input of 9,000 Btu to the highest 199,000 Btu. With a state-of-the-art design, the Greentherm 9000, with the use of a Wi-Fi connection and corresponding app, you can remotely activate the recirculation pump, check out the energy usage and control the temperature.

Both models come with a warranty of 15 years.

Tankless advantage

Bosch water heaters with tankless technology heat water on demand and deliver it non-stop without interruption, saving up to 50 % of heating costs. For the homeowners who prefer freshwater, available any time and in endless supply, tankless technology is the solution. Since tankless heaters do not utilize the storage tank and heat water when there is no demand, standby heat loss is eliminated so users can enjoy more savings.

You don’t have to wait for the water tank to fill up and then heat and deliver or recover from the previous use. With tankless, hot water is heated directly and is available almost immediately. As some will complain that the flow rate is limited, some manufacturers offer a solution by linking two or more units into one system and therefore provide more hot water.

If it takes longer for hot water to reach the tap, Bosch offers tankless models with the circulation pump built-in and recirculation system. Check out the Greentherm 9000.

All the models offer 100% serviceable parts, so even if the heater fails and there is no hot water, it is superior, more cost-effective, and environmentally friendly to replace the malfunctioning component. No need to throw the whole unit away, as it would happen with the tank-type model if it is leaking, for example.

Yes, they cost more than the conventional type but they last longer, have lower operating and energy costs, are more convenient to use, provide enhanced comfort, and better overall experience.

Bosch electric tankless

Bosch Tronic

Bosch Tronic electric tankless water heaterBosch Tronic

Bosch Tronic is the series of small electric tankless water heaters designed for whole-house and point-of-use applications, such as smaller homes, apartments, and cottages.

The largest model, WH36, from the 5000C series, provides endless hot water to up to 3 major applications. They are designed small and compact, allowing installation virtually anywhere inside the home or business, while the powerful and efficient heating elements ensure plenty of hot water.

There are a few models available, where most of them are tankless, except the last one mentioned below:

  • Tronic 6000/5000 – available in three sizes (WH36, WH27, and WH17) can be used for the whole-house application.
  • Tronic 3000 – available in five sizes from US3 to US12 and are known as under-sink or point-of-use (POU) models, and mostly one fixture.
  • Tronic 3000T – available in three tank sizes, ES2.5, ES4, and ES8, and designed for point-of-use service.

The largest electric model, WH36, with its 36 kW of power, can provide endless hot water to up to 3 major applications. With the small, lightweight (26.5 lbs.), and compact design, they can be installed virtually anywhere inside the house. Due to their effective and efficient operation, they can be used in whole-house applications.

The warranty on the Bosch electric water heaters is 5 years.


The most advanced model from Bosch, Greentherm 9000, released in 2017, could achieve the “industry highest” energy factor of 0.99 and thermal efficiency of close to 100%.

Moreover, let’s not forget that the average life expectancy of the Bosch tankless is over 20 years, with a warranty of 15 years. The advanced design offers some fantastic features such as innovative technology and advanced electronics that provide stable and accurate temperature, computerized control, and diagnostics.

About Bosch

Bosch is a German manufacturer of HVAC products for residential and commercial applications, building quality products since 1886. In North America, you can find several brands in the tankless category, as mentioned above, while in Europe, Bosch tankless hot water heaters are known as Junkers.


Bosch tankless water heaters, no matter whether they are powered by gas or electricity, utilize many advanced features and sophisticated technologies. This results in superior on-demand water heating, lower operational cost, and ultimate pleasure with an endless supply of hot water.

Due to the tankless design and the built-in modulation, they ensure constant temperature and enhanced comfort. Mini tanks, on the other side, are used mainly for point-of-use applications and for small jobs, as they produce only low volumes of hot water.


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