This article contains affiliate links. If you click on these and make a purchase, we may receive a small percentage of the sale without any additional costs to you. Read our privacy policy to find out more.

Bosch Therm 940 ES Review – (Non-Condensing / Natural Gas)


Bosch-Therm-940-ES-ReviewConsidered Bosch’s highest capacity non-condensing natural gas tankless water heater, the Bosch Therm 940 ES NG has a maximum BTU input of 199,000. Replacing the Bosch GW #715 ES and the Bosch Aquaster 2700 ES, this tankless gas water heater seems to have a better overall performance than its predecessors.

The electronic ignition system within the Bosch allows for significant savings on your energy bill and a consistent flow of hot water. Over time the savings from a tankless gas water heater makes spending a little more upfront on this model quite worth it.

Being able to receive endless, hot water on demand is exactly what a tankless gas water heater promises. The Bosch Therm 940 ES can live up to these expectations and more. The flow rate on this model is 7.15 gallons per minute, with a 9.4 flow when at 35 degrees and a 6.0 flow at 55 degrees. To place this in perspective, it normally takes 4 gallons per minute when running a shower plus an appliance simultaneously. The GPM or gallons per minute in the Bosch 940 can run more than one shower plus several appliances and all are receiving hot water. This 67-pound model holds its own when it comes to the consistency of hot water and the volume it can produce.



Trustworthy Brand

The Bosch Therm tankless natural gas water heater models are backed by a relatively familiar household name. This Energy Star certified water heater of this series is highly energy efficient for those looking to save on cost and space. It can save nearly 40% or close to half of your energy bill. Measuring the efficiency of a tankless heater is done by measuring the amount of hot water transfer from the model to the faucet.

Hot Water Supply

The idea of endless hot water is through taking the water you are running and sending it through the internal heating system. By not running heat when not in use, the energy level used to work the tankless water heater is significantly reduced. Since it is not like the conventional heaters with tanks, it does not hold water idly. There is wasted energy when maintaining hot water in the water heater tanks, particularly when they are not in use. The Bosch Therm 940 ES Natural Gas Tankless Water Heater operating on this efficiency level makes it ideal in reducing your energy bill.


Installing the Bosch 940 is flexible as well as an energy saver. For one, the energy efficiency is maintained at 83% thermal. This Energy Star certified model uses a secondary heat exchanger. This means more heat is being extracted from the combustible gas, which cools the water to a condensation point. This means an added piece of equipment, a PVC pipe, is required.

The combustion is sealed and the heater offers dual fan technology. This allows for the heater to vent through a side wall or the roof. The option to install in more than just one place is definitely appealing when switching over from a more conventional water heater. Being able to open up space by placing discreetly out of eyesight is a major positive. You have to keep in mind that with this being a natural gas tankless water heater, there will be some slight restrictions where the placement of this model will work.


There are great safety features to this Bosch 940 ES. The built-in freeze protection allows for it to know when to shut down if the maximum temperature is approaching. In addition to this protection, there is also a built-in water filter. Note that hard water can place some lasting damage to your unit. Therefore having a filter to soften the water will add to the longevity of the equipment.

Check The Latest Price on Amazon!


Bosch-Therm-940-ES-pros-consWith this being a non-condensing model, a stainless steel venting system is necessary. Using a non-condensing tankless gas water heater means the heat exchanger to heat the water on demand. This is one of the reasons going on-demand can be such an efficient decision. However, with being non-condensing, there is a need for special equipment.

The gases pushed out are normally around 300 degrees. A stainless steel venting system provides protection against the extremely high temperatures and possible corrosion. The downside is this additional protection can run you more cash than anticipated.


Besides the cost of additional equipment, the installation requires more care and can come with a higher priced installation. With it not necessarily being the simplest install for a novice, going the professional hire route would be highly recommended.

The tankless water heater does run at a higher price point than most conventional options. The advanced system reduces energy use with heating the water when it is in use. The upfront cost of the equipment may cost more, however, looking at the overall savings on your energy bill; one can argue that it evens out.

Sizing does matter

The way the on-demand is set up, it does heat water differently than the conventional heaters. The lag time in heating your water may occur. Some find it as a deal breaker on purchasing a tankless water heater altogether. Selecting the right size water heater for your home is critical to receiving the most out of your purchase.

Typically, if you plan on running the shower plus one or two appliances, a 4 GPM heater would suffice. With this model, the Bosch 940, you end up with 9.4 gallons per minute. This allows you to take more than one shower and run a few appliances and having more than enough hot water.

Check The Latest Price on Amazon!

Final Thoughts

The Bosch Therm 940 ES Tankless Natural Gas Water Heater is

  • Compact, space saver
  • Energy efficient
  • Backed by safety features

If you are looking to provide hot water for a larger home or have heavy use on several appliances, this model would be a nice option to consider. There are a few more upfront costs as far as installation and additional equipment are concerned. Combine that with this model being mid to high price range, this is an investment you have to carefully consider. With the 15 year warranty for residential use and the average lifespan of tankless gas water heaters being around 20 years, this may be an investment worth making.

by Water Heater Mag

Leave a Comment