Bosch Tankless Water Heaters

For consumers, the lower operating costs and constant comfort of a tankless water heaters make it the rising star of home appliances. For manufacturers, the growing demand makes tankless water heaters a hot (no pun intended!) industry to invest in. The Bosch Group company was founded in 1886 in Stuttgart, Germany, and today has more than 300 subsidiaries in over 150 countries. While the brand is fairly diverse covering industries such as automotive, industrial technology, consumer goods, and building technology, its thermo-technology subset is pretty innovative in its approach to making the best tankless water heaters.

Bosch claims the best warranty in the industry for its tankless water heaters. Most of the heaters reviewed below offer a 15-year limited warranty on the heat exchanger, and a two-year warranty on all other parts. But, as always, be wary of how far a limited warranty will actually get you—freezing may not be covered, or if your water is too hard and causes quick scale buildup, it might compromise your warranty. We strongly encourage you to find installation manuals online and read each warranty for yourself to ensure you know what you’re buying, since this isn’t a small purchase for your home.

With that being said, Bosch is pretty impressive across the board with its options for tankless water heaters, balancing price and features nicely. We have done the hard work of rating Bosch’s line of tankless water heaters. We’ve picked a few that we think stand out for their unique features—read on to find out more!

Bosch Tronic WH27 Electric Tankless Water Heater

Bosch has labeled this tankless water heater as a whole-home heater—but note that it is made to heat water for one major appliance at a time. If you have a small home with light hot water demands, or if your home has between one and three occupants, this would be a good fit for you. Other suitable applications include an office unit with a small bathroom attached, an in-law suite, or a garage apartment. You will have to get used to using just one hot water demand at a time—don’t run the dishwasher and the clothes washer at the same time, for instance, or you’ll just have cold water washing your dishes.

Due to its smaller capacity and its electric heat source, the Tronic WH27 is cheaper than even the low-end gas-powered models. In the electric model price range, it falls about in the middle. With a 55-degree temperature rise (common for warmer climates) you can expect a max of 3.3 gallons per minute (GPM) of water flow. It gets an impressive 97% efficiency rating, so it is Energy-Star certified.

The Tronic WH27 is a 240-volt tankless water heater, and if lesser voltage is used, you will have reduced electric output ability in the heater. The WH27 requires 120 amps of electricity. For installation, 120 amps would be supplied through three 40-amp double-pole breakers in your breaker box, so check to make sure you have the space available. Your house must have at least a 200-amp service, which older homes likely don’t have.

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Bosch Therm 330 PN NG Natural Gas Tankless Water Heater

For those looking for a good tankless water heater in a small residential setting, the Therm 330 PN might be just the right fit. You will find this natural gas heater at the mid point of the price range.

The Therm 330 has a manual Piezo ignition system that starts the heater without an electrical connection. It’s really best for those with one or two occupants who use a low volume of hot water, and are okay with using just one major appliance at a time. You can expect to see about 3.3 GPM of water flow in a 35-degree temperature rise, which is really a ground water inlet temperature of 70-80 degrees Fahrenheit.

This spunky little heater operates with about 77% thermal efficiency, and a 0.68 energy factor. Especially helpful to know is that if you have a home with ½-inch gas line connections and you don’t want to deal with the costly upgrade of installing ¾-inch pipe that some other tankless water heaters require, the Therm 330 PN NG would be an option to consider. The max output on the Therm 330 PN NG is 75,000 BTUs. For installation, it also easily vents with a galvanized B vent and a natural draft.

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Bosch Therm 520 HN NG Natural Gas Tankless Water Heater

This Therm 520 HN NG from Bosch is definitely one of a kind. Bosch is looking to attract a very specific customer with this whole-house tankless water heater. It is a non-condensing natural gas unit, with max a BTU of 117,000, and it’s designed for indoor use. The real unique factor is in the ignition source—this unit uses no electricity or gas to start the heater. Instead, a water-powered turbine uses the water flow to ignite the burner.

This battery and electricity-free ignition means that this heater is the perfect fit for remote homes or spaces without access to electricity, or even areas with more rough or stormy weather or power outages. Have a hunting cabin or rustic getaway tucked away from society? The Bosch Therm 520 HN NG would be a great fit for you. You will still need to have natural gas access to fuel the heater, but for the ignition itself, it’s powered without it.

A few of the little details: you’ll get an Energy Factor of 0.78 with this heater, and you can expect it to power two appliances or hot water taps at the same time. With a 35-degree temperature rise (for those in very warm climates, with an incoming water temperature of 70-80 degrees Fahrenheit or above), you can expect 5.2 GPM of water flow. For a 55-degree rise, capacity would be at about 3.4 GPM. That patented technology from Bosch does push the Therm 520 HN NG’s price to the mid to high end of the natural gas line, but it’s still a fairly reasonably priced whole-home heater.

Bosch Therm 520 HN LP Liquid Propane Tankless Water Heater

This Bosch Therm 520 HN LP is a really unique tankless water heater. Bosch is looking to attract a very specific customer with this whole-home model. It is a non-condensing liquid propane unit, with a max BTU of 117,000, and it’s made to be installed indoors.

The real unique factor is the ignition source—this unit uses no electricity and has no standing pilot light to start the heater. Instead, a water-powered turbine uses the water flow to ignite the burner. That patented technology from Bosch does put the Therm 520 HN LP’s price in the middle of the price range of the propane tankless water heater line, but it’s still a fairly reasonably priced whole-home heater. This battery and electricity-free ignition means that this heater is the perfect fit for remote homes or spaces without access to electricity, or even areas with more rough or stormy weather or power outages.

Have a hunting cabin or rustic getaway tucked away remotely? The Bosch Therm 520 HN LP would be a great fit for you. You will still need to have propane access to fuel the heater, but for the ignition itself, it’s powered without it. You’ll get an energy factor of 0.78 with this heater, and you can expect it to power two appliances or hot water taps at the same time. With a 35-degree temperature rise (for those in very warm climates, with an incoming water temperature of 70-80 degrees Fahrenheit or above), you can expect 5.2 GPM for your water flow. For a 55-degree rise, this capacity drops to about 3.4 GPM.

Bosch Therm 520 PN LP Propane Tankless Water Heater

When you’re searching for a tankless water heater, it can be hard to discern the simple differences between various models. First, let’s talk about price. The Therm 520 PN LP falls right in the middle of the price range, and is a good option for propane users.

The Therm 520 has a manual Piezo ignition system that starts the heater without an electrical connection. It’s really best for those with up to three occupants who use low-to-average levels of hot water, and are okay with using just one or two major appliances at a time. You can expect to see about 5.2 GPM of water flow in a 35-degree temperature rise, which means a ground water inlet temperature of 70-80 degrees Fahrenheit in a fairly warm climate. You can check online or possibly with your water provider to see what your incoming groundwater temperature is. At a 55-degree temperature rise, you’ll get a water flow of about 3.3 GPM.

Make sure you install the Bosch Therm 520 PN LP indoors. It will give you about 78% or more thermal efficiency, and you can expect a max BTU of 117,000. For installation, it also easily vents with a galvanized B vent and a natural draft.

Bosch Therm 330 PN LP Propane Tankless Water Heater

For customers who are seeking the best tankless water heater for a smaller residential setting, the Therm 330 PN might be just the right fit. You will find this liquid propane heater in the mid-to-high section of the price range.

The Therm 330 has a manual Piezo ignition system that starts the heater without an electrical connection. It’s really best for those with up to two occupants who use lower levels of hot water, and are okay with using just one major appliance at a time. You can expect to see about 3.3 GPM of water flow in a 35-degree temperature rise, which is really a ground water inlet temperature of 70-80 degrees Fahrenheit.

This spunky little heater operates with about 77% thermal efficiency, and a 0.68 energy factor. If you have a home with ½-inch gas line connections and you don’t want to deal with the costly upgrade of installing ¾-inch pipe that some other tankless water heaters require, the Therm 330 PN LP would be an option to consider. The max output on the Therm 330 PN LP is 75,000 BTU. For installation, it also easily vents with a galvanized B vent and a natural draft.

Conclusion

Remember, there is no single best tankless water heater because everyone’s setup is different. Some of the Bosch heaters might be nice for families with older homes that need to replace a water heater tank, have a smaller space, or have older gas lines that are half an inch in diameter instead of going for some of the higher-capacity heaters that require 3/4-inch pipe.

The Bosch tankless water heaters in our review have impressed users with their ability to innovate and provide non-electric ignition starts in a variety of ways. While we know you’ll still have to use a gas source to power the unit, it is a nice option for those who want to live off the grid. Those who use solar or wind power with standby options for propane or natural gas would do well to choose a tankless water heater from the Bosch list above.

More than anything, we want you to have all the facts for each fuel source and brand that you might be considering in a comparison of tankless water heaters. We have scoured listings and websites, installation manuals, and warranties to find out all we can about installation, price, features, and the reliability of each brand and product we review. Sometimes it can be hard to find specific information about the variances between models and brands, and we hope that you have found all that you are looking for when you read our reviews.