Powerstar Tankless Water Heater

Review of Bosch Powerstar AE3.4, AE7.2, AE9.5, AE12 for point-of-use service

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Powerstar water heaters are electric tankless appliances for point-of-use service designed by German manufacturer Bosch. With four models available these electric units can be installed and very conveniently used for small hot water jobs.

Great advantage of electric and on demand point-of-use units is the elimination of a long pipe that runs from a distant whole house water heater which reduces heat and energy loss significantly.

Bosch Powerstar point-of-use models are built to deliver an instant hot water to one specific plumbing application, like shower or kitchen sink, and therefore the best location is under the kitchen sink or bathroom. With such an installation you don't have to wait 2-3 minutes to wash your dishes and waste water; it is saving you time and money.

Note: Point of use Bosch Powerstar water heaters are designed for indoor installations and in the room where there is no chance of freezing. The only way to fully protect your water heater is by removing it completely from such exposure.

Model reviews

bosch powerstar electric water heater ae12

Bosch PowerStar water heaters for point of use service are instantaneous electric units with 99% thermal efficiency and with one goal, to supply you with an endless hot water at the spot and where demand is.

Based on the flow rate these small Bosch electric water heaters provide and temperature rise, there are 4 different models to choose from: AE3.4, AE7.2, AE9.5 and AE12, where number shows the heating power output (i.e. AE3.4 have heating elements of 3.4 kW).

Because of its compact and small design, they will save you valuable room space, with the option to install horizontally and vertically, virtually anywhere; in your home, small office, store, both residential and commercial applications (model AE12 installs horizontally only).

All these tankless models require 220/240 V except model AE3.5 that requires 110/120 volts; and based on the model, required amperage is from 29 to 50 A. Difference in amperage allows you to choose between low and high temperature setting.

Example: Powerstar AE 7.2 model has low setting of 3.05-3.6 KW with the 15 amps, and its high setting is from 6.1-7.2 kW with 30 amps. Model AE9.5 can go from 3.5 to 9.5 kW maximum heat output.

For Powerstar electric water heaters to function correctly, water in your home plumbing pipes has to be between 0.7 bar min (1.4 bar for AE12) to 10.3 bar max. (10 (20 for AE12)-150 psi).

Be aware that your hot water outlet temperature doesn't depend on the setting only, but the incoming water temperature as well, so your unit might need temp. adjustments during the year (put on maximum during the winter).

Temperature is factory set to 45 C or 113 F, and if you are using Bosch AE12 model use the Adjustment Spindle to adjust to the desired temperature.

For other models AE3.5, AE7.2 and AE9.5 use the Power Selector Screw that allows you to switch between low - LO and high - HI settings.

If you choose LO, only one heating element is operating and the output will be half power. Full power comes with both heating elements working at the same time; you just have to set the screw on HI.

All models are equipped with a safety device called thermal cut-out, mounted on the heat exchanger. It cuts the power to heating elements if the water flow is reduced too much and temperature goes above allowed.

To reset the water heater back, so it can heat again, there is a manual reset button inside the unit.

Review and consumer reports

Here is the summary of dozens of consumer reviews collected from different sources like Amazon, Buzzillions, Home Depot and other online stores and customer review sites.


  • Instant hot water, works quickly.

  • Easy to install.

  • Space saver and fits neatly in the kitchen or bathroom cabinet.

  • Cheaper than traditional tank type water heater.

  • Solid copper heat exchanger has 5-year warranty.

  • If you need any part replacement, you are covered for 1 year.


  • After unit has been used recently there is a short burst of hot water unless run the water for a few seconds to settle down the temperature.

  • No temperature setting button, have to use screwdriver.

  • Technical support is slow, long phone-call holds.

  • Frequent quality issues even with brand new units.

  • The temperature may fluctuate because water pressure.

  • To reset the breaker you have to take the cover off.

  • Needs thermostat control.

To buy Powerstar electric tankless water heater you have to pay between $190 and $269 for the brand new one and depending on the store, or cheaper around $130 and up for factory refurbished unit.

(Pictures courtesy of Bosch)