Bosch tankless water heaters are some of the best tankless water heater units currently on the market. Unlike other top brands, such as Noritz, Rinnai, and Paloma, Bosch tankless water heaters have been designed specifically with the US market in mind. As a result, they tend to be easier to install than some other brands.

Gas and Electric Models

Unlike Noritz and Paloma, which only have gas tankless water heaters, Bosch offers both gas-powered and electric-powered tankless water heater models. Like other brands, Bosch's gas-powered tankless water heaters are able to provide an endless supply of hot water for multiple showers and appliances in a home. These models are ideal for larger families.

Although not as well known as gas-powered tankless water heaters, electric tankless water heaters are actually far more energy efficient (98% efficient, compared to the 80 – 84% efficiency of a comparable gas-powered model). However, the Bosch PowerStar AE125, the larger of the two electric tankless water heaters, provides only 3.7 gallons of hot water per minute. At 105 degrees Fahrenheit, that means consumers can use the water heater to provide heat for just one shower at a time. The Bosch electric tankless water heaters are ideal for someone living alone or with just one other person who doesn't need to shower at the same time.

Bosch AquaStar 2400ES Gas Tankless Water Heater

The Bosch AquaStar 2400ES is Bosch's flagship model. With an efficiency rating of 82%, it is not as efficient as some of its competitors, but it still qualifies for a Recovery Act tax credit, making it a smart purchase for most families. As Bosch brags on its website, the AquaStar 2400ES can save your family up to 50% on your monthly energy bills. If you get the federal tax credit, plan on staying in your home for more than a few more years, and use a lot of hot water, the Bosch AquaStar will quickly pay for itself.

Point-of-Use Bosch Products

Bosch's Ariston Mini-Tank Point-of-Use tankless water heater installs directly at a sink to provide instant hot water. Electric powered, the Ariston Mini-Tank can be installed in a small, enclosed space with zero need for any type of ventilation (unlike the large, gas-powered AquaStar). Point-of-use tankless devices eliminate any need for wasting cold water while you wait for the water to warm up. Another way to use Bosch's point-of-use models is to place it in-line with your main water heater. By the time you exhaust the supply in the smaller, point-of-use water heater, the larger water heater is ready to start providing hot water for other applications. You can think of this method of using a point-of-use tankless water heater as the “hybrid car” of the water heater world.

If you're interested in purchasing a Bosch tankless water heater, choose the model that's appropriate for your situation by visiting the “Product Selector” section on their website. By asking a few simple questions, the website automatically eliminates the products that aren't right for you, thus making your research into Bosch's products easier and quicker.

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"I hooked this up in the kitchen sink to avoid a 30 foot run from the main HWH. It took about 1 hour under the sink and another 30 minutes installing another power outlet. The heater works great. The 2.5 gallon supply is plenty to handle dishes and hand washes. I disconnected the main supply and have not missed it."  Amazon.com Consumer G. Austin

Many consumers have a need for small capacity water heaters located a distance away from the main water heater installation, for example in an outlying washroom. This situation poses special problems in delivery because for hot water to reach the end user, hot water must travel a large distance from the main heater. This causes increased water usage and wasted energy. The Ariston tankless point-of-use water heaters from Bosch are specifically engineered to solve this problem. They are small electrical water heaters installed at the point-of-use and provide nearly instantaneous, endless hot water, eliminating the need to wait with the water running while hot water comes all the way from the main supply tank.

The Ariston GL2.5, GL4, and GL6+ heaters have tank capacities ranging in size from 2.75 to over 6 gallons, and provide a recovery rate of 6.8 gph with a rise of 90ºF. As a result, these heaters are ideal for bathrooms located at the far extremes of a home's plumbing system. The electrical power requirement on all Ariston models is 1500W, pulling 12.5 amps at 110V, and easily plug into an existing standard household outlet, making installation incredibly easy for the DIYer. The heaters are thermostatically controlled, providing outlet temperatures from 65º to 145ºF, and can be mounted either horizontally or vertically. Size ranges from about 10"x10"x12" for the GL2.5 and GL4 to 10"x10"x17" for the GL6+ and come with heavy gauge steel enclosures.

Depending on tank capacity, the Ariston water heaters come supplied with either ½" or ¾" NPT pipe fittings. All models have pressure ratings of 150 psi, and are constructed with glass lined tanks equipped with pressure relief safety valves. Bosch offers a 6 year warranty on the tank and a 1 year warranty on everything else.

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Bosch's PowerStar series of tankless water heaters are electric water heaters -- no gas connection is necessary. This makes them highly efficient. The AE115 model has an energy efficiency of 90%, while the AE125 has 94% efficiency. They are intended for light residential use, and provide hot water to one outlet at a time,. The AE115 has a maximum flow rate of 2.6 gallons per minute, at a degree rise of 45 degrees Fahrenheit, while the AE125 can provide 4 gpm at the same rise. This means that the AE115 is not ideal for use with bathtubs, although it can handle most other light residential requirements, such as one sink, dishwasher, washing machine, or shower. Temperature is controlled by an external knob, and the PowerStar heaters can deliver water at up to 131 degrees Fahrenheit, although 105-115 degrees is best for efficient performance and flow.

Both units are extremely compact, checking in at 15.2" x 15.5" x 4.2", but can replace a standard 50- or 80-gallon tank heater. This small size means that the PowerStar heaters can be mounted almost anywhere and in any direction.

The AE115 activates with a flow rate of .6 gallons per minute, while the AE125 activates at .8 gpm, so they begin providing hot water quickly after the flow begins and waste less water. Bosch estimates that these heaters will provide a savings of up to $45 annually as compared to standard tank heaters.

The AE115 is not recommended for areas where the average annual ground water temperature is less than 60 degrees Fahrenheit, which in the United States restricts it mostly to the South and Southwest. The AE125 is necessary for cooler climates.

In both models, the heat exchanger is solid copper, with poly heating elements, providing an estimated lifespan of 20 years. Bosch offers a ten-year warranty on the heat exchanger and a one-year warranty on the remainder of the unit.

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Bosch's AquaStar 125 series of tankless water heaters are intended for light residential or small business use. Each AquaStar heater is meant to replace a 40-gallon tank heater and supply hot water to a single major water outlet at a time, such as a shower or a dishwasher. The maximum flow rate for the AquaStar 125 series is 4 gallons per minute at a degree rise of 45 degrees Fahrenheit, and the manufacturer recommends a water pressure between 30 and 15o psi.

"I installed a Bosch Aquastar 125B that burns natural gas. I have had it two years and it already paid for itself.  What I like about the unit: Installation was easy. The unit is small, lightweight and constructed well of high quality materials. Can be mounted on a wall to free up valuable space. You have an endless supply of hot water. I am able to run my washer and shower at the same time with no problems. My natural gas usage is less than 2/3 of what it was with the tank water heater. Saves money. Has a very small pilot that can be turned off if you go on vacation or whatever and can be easily re-ignited with the press of a button. What I don't like about the unit: Requires a 5" vent pipe. Unable to run a trickle of warm water.  While the initial investment seems high, the unit has paid for itself. The good points such as energy savings and money savings definitely outweigh any negative aspects of the water heater. I hope that this information is helpful for anyone who may be considering the purchase of such a water heater."  ConsumerReports.org Reader Joe V.

Besides the basic 125B model, the AquaStar 125 series includes the AquaStar 125BO, which is intended for outdoor mounting. It has freeze protection down to 5 degrees Fahrenheit. Also in the series are the AquaStar 125FX, which incorporates a power vent for horizontal and sidewall venting, and the 125HX, which uses the flow of water to provide the energy for ignition and so requires neither a gas pilot light or an electric igniter, saving even more on energy. All models in the 125 series can use either natural gas or liquid propane.

While the AquaStar 125 series does not have an EnergyStar certification, Bosch estimates the energy savings for using one to be between $100 and $200 a year, compared to tank heaters. The AquaStar 125 series has an energy efficiency of 82% (80% for the 125FX).

The AquaStar 125 series is designed with durability and ease of maintenance in mind. The internal parts that transmit the water are either solid copper or solid plastic, and all of these can be replaced and/or recycled, making it easy to keep your heater going even after parts wear out. The exterior casing is made of stainless steel and aluminum, with a baked epoxy finish; the burners are also stainless steel.

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The Bosch Model 1600P Tankless Water Heater is designed to replace the 125B model and is available in both Natural Gas (NG) and Liquid Propane (LP) types. It can deliver, at a minimum, 2.1 gallons of hot water per minute at a 90 degree F temperature increase up to a maximum of 4.3 gallon per minute at a 45 degree F temperature rise.

It has a capacity to vent vertically using a 5” flu size type-b double wall vent. Horizontal venting can be made available for this model by availing of an optional accessory Model - AQ4 which is a power vent with built-in freeze protection.

The 1600P is designed to provide unlimited hot water for just one major outlet at a time. This means that one unit can only be used for a shower and a separate unit has to be purchased for the other outlet in the house.

It operates on Standing Pilot ignition contrary to the 1600H model which operates with Hydro-generated ignition.

Being a 117,000 BTU (British Thermal Unit) AGA certified, this model is definitely a powerful heating system that can heat up water fast using less energy. This results in big savings on electricity. In addition to this, it only runs when used so savings on utility costs can reach up to 50% annually.

The minimum flow needed to activate the heater is 0.5 gpm.  It has a modulating gas valve to control temperature and a pressure relief valve to limit the pressure in the system on instances of equipment failure. With a product dimension of 8.5D x 16.8W x 25.8H inches and a weight of 33 pounds, the 1600P is lightweight and compact and can be mounted on the wall. This makes it a logical choice for people who do not have space to spare for a bulky water heater. Among its other specifications are thermal efficiency of 78% for both NG and LP and energy factor of 0.69 for NG and 0.79 for LP.

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Many owners of smaller homes and cottages are looking to install tankless water heaters instead of conventional storage water heaters. The Bosch Model 1600H tankless water heater is engineered to supply smaller demand installations with a minimum of installation issues. The 1600H is unique in that no electricity is required for ignition, adding to the benefits derived from the use of a tankless water heater system.

The Bosch Model 1600H is supplied as either a natural gas or LP powered unit with a maximum input power of 117,000 BTU. Minimum flow rate required for activation is 0.6 gpm. The 1600H can supply 2.1 gpm with a 90°F rise, however, this is derated to 45°F at 4.3 gpm. Efficiency of the 1600H averages 80%, and energy savings can be expected to be approximately 50% over conventional heaters.

Bosch has developed an innovative method for powering the ignition circuitry of the 1600H. The heater requires no electrical supply and has no standing pilot light. Instead, the heater has a small micro-turbine electrical generator built into the water openings. As water flows through the unit, the turbine spins and generates electricity which is then used to ignite the gas/air mixture.

Accessories include a power vent for horizontal venting and a vertical vent kit. The exhaust uses a conventional 5” B Type double wall galvanized vent pipe. Water connections are ½" Male NPT fittings, and the heater can handle inlet water pressures ranging from 30 to 150 psi. The 1600H features a solid copper heat exchanger, and stainless steel burners. Safety features include a flame failure device, pressure relief valve and over heat prevention.

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Many homeowners faced with increasing energy costs have decided to install tankless water heaters to completely supply all the hot water needs of their household. The Bosch AquaStar 2400ES tankless water heaters are engineered to provide enough hot water for two simultaneous applications, save roughly 50% on energy costs and have an estimated life of over 20 years with an 82% efficiency rating. The heaters are supplied in either natural gas or LP versions.

The 2400ES has a maximum energy input of over 175,000 BTU/hr and can supply a maximum of 6.4 gpm with a 45˚F temperature rise. This performance decreases, however, as the inlet water temperature decreases, yielding 3.2 gpm with a 90˚F temperature rise. The minimum flow rate to activate the heater is 0.65 gpm. Both inlet and outlet water connections are ¾" NPT standard fittings.

Another benefit of this model is that there is no standing pilot light. Ignition is completely electronic and powered by a conventional 120V household outlet. Outlet temperatures are thermostatically controlled and variable from 100˚F to 140˚F with a default setting of 122˚F.

The Bosch Aquastar 2400ES features a forced exhaust system. As a consequence, the heater vent can either be terminated horizontally or vertically. Exhaust piping is 3" diameter and must be stainless. The heater also offers a sealed room feature where not only exhaust is vented outside, but combustion air is brought into the heater via separate piping (either 3" PVC, aluminum, or galvanized metal) from the outside as well. Safety features include a flame failure device, pressure relief valve, over heat prevention, and monitoring of both inlet and outlet temperatures.

Bosch offers a 12 year warranty on the heat exchanger in a regular single-family residential application. This drops to 5 years in a recirculation system and 2 years in other, non-residential applications. All other parts are warranted for 2 years.

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"We purchased this water heater because ours broke on thanksgiving last year. So far this one has been quite a bit better than the one we replaced. I installed this unit myself which was pretty easy. If you are moderately handy you should have no problems. The temp is right on the money and the water gets hot pretty quick. The only thing that has happened so far that I thought was lame is that we had a power outage a few weeks ago and when the power came back on the heater didn't. I had to go outside and reset it myself. If that's the only thing that ever goes wrong I'll be happy."  ~RateItAll.com Consumer Marcus Kubath

With the Bosh AquaStar 2700ES Tankless water heater, it is possible to run three hot water applications at once efficiently, running at seven gallons per minute- for instance, washing clothes, running the dish washer and showering. Carrying an overall energy factor of .82 for liquid propane and for natural gas, this means a thermal efficiency of eighty two percent. Almost providing a seemingly endless supply of hot water, the Bosch AquaStar 2700ES Tankless unit has a direct vent room sealed combustion, as well as a 19,900 BTU power input, with both natural gas and liquid propane.

The unit also has a solid copper heat exchanger, primary fan, secondary air fan, lcd display and a control unit that are made solidly of materials that carry the Bosch name with pride, adding to the overall energy efficiency. Opting for wireless remote control thermostat, you can program the heater for any temperature that is needed and easily change temperatures at any time. In approved climates, an outdoor installation kit may be available and offers a twelve year warranty on a heat exchanger for that purpose.

Using a 120 volt plug in with no standing pilot as well as a gas and water connection with a male NPT adapter, the unit is easily installed in most homes with a minimum water pressure of 30 psi, or a maximum of 150 psi. Because the Aquastar 2700ES is only 30.5” by 17.875”, and 11.25” in diameter, it is very compact and can be installed in almost any closet or space without being obtrusive, compared to more traditional hot water heaters, this weighs in at a mere seventy five pounds. This unit in particular also boasts up to a fifty percent savings in energy costs, and a tax rebate may also be available to further reduce costs.

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