Condensing Water Heater Reviews: A 2020 “Best of” Expert Comparison

If you’ve been hunting for a condensing tankless water heater that runs on either natural gas or propane, we’ve got 5 of the very strongest models here for you to choose from.

None of these units is especially cheap but in return for your investment, you’ll get the best in energy-efficiency along with top-tier performance.

If you want to get rid of that tank-style heater, we’ve got a direct replacement on our list, too.


For on demand water the easy way, we’ll launch in with the first of a pair of Noritz water heaters.

1) Noritz NRC66 DV NG Indoor Condensing Tankless Water Heater

In the tankless water heater industry for over a half century, Noritz serve up a pricey but highly effective condensing model ideal for indoor installation.

Heating water on demand using natural gas, this heater then uses electricity for ignition, powering electronics and preventing these electronic components from freezing.

Where many of these heaters call for expensive stainless steel venting, you can take care of business using schedule 40 PVC winning back a little cash from that stiff sticker price. You could also use PP or CPVC.

If you prefer to mount this unit on a non-exterior wall, there’s a non-direct conversion kit available to make this possible.

With a maximum flow rate of 6.5 Gallons Per Minute, this heater is a class-leader.

You can hit 93% efficiency whether to choose to run this heater with natural gas or propane. While flagged as low NOx, it doesn’t quite meet industry standards on this front.

Weighing just 38 pounds and occupying a small, slimline footprint, you can mount this model just about anywhere.

The pair of heat exchangers are laden with safety features and warrantied for 12 years.

The remote thermostat is a nice touch and streamlines control a treat.

While this model undeniably burns gas with great efficiency, it also manages to draw down a great deal of electric power. In a larger home, you’ll struggle to service 2 showerheads simultaneously so you should be clear about your intended usage before committing to purchase.


  • Perfect for smaller 2-bathroom homes in the southern states or 1.5-bathroom homes where the climate is cooler
  • Relatively straightforward installation with DIY a viable option
  • Compact design and super-quiet in operation


  • Slight delay in hot water delivery since there’s no recirculation pump

2) Noritz EZTR40-NG Condensing Tankless Heater

Have you got a 40-gallon or 50-gallon tank water heater in need of replacement?

If so, this replacement unit from the stellar Noritz will slot in neatly and give you endless on-demand water without the cost and inefficiency of keeping reserves permanently heated up.

You’ll get everything you need for installation bundled and the standard ½-inch gas line connection makes this heater perfect for replacing your tank-style heater with no need to start altering the gas lines.

Energy-efficient to 89%, you’ll benefit strongly from switching from your old tank heater to this tankless variant. With electronic ignition, you’ll also sidestep the need for an always-on pilot light. For this, you will need a 120V/60Hz power source so make sure that’s in place.

It’s a disappointment that the remote control is sold separately since taking charge without this is awkward and inconvenient. You’ll also need to get the cord separately so factor this in when budgeting.

Since the supplied venting can be pushed through the B-vent already in place, you’ll save yourself time, money and hassle when it comes to installation. This is a small but valuable touch.

You’ll get the usual attention to detail from Noritz with safety features. From flame sensor and overheat prevention through to safeguards against lightning and freezing, you can rest easy and let the heater do all the work without worrying about any accidents.

With a concentric direct vent that comes rated zero-clearance and a slimline form factor, if you’ve got a fluid budget and fancy uprating your water heater, this makes a smart choice.


  • No need to rework water connections or up-size the gas line
  • Innovative venting system runs inside existing metal B-vent
  • High-efficiency condensing and maximum flow rate of 6.6 GPM


  • As with all Noritz heaters, this is not particularly cheap but it does represent excellent value

3) Rheem RTGH-95DVLN Indoor Natural Gas Water Heater

Ramping up the energy-efficiency even further, the Rheem RTGH-95 DVLN has a 94% rating thanks to the remarkably powerful stainless steel condensing heat exchanger in place.

While natural gas is used for fuel, the highly intelligent electronic controls help keep safety uppermost while maximizing efficiency.

This Rheem tankless water heater is expressly designed for larger homes with a constant and heavy demand for hot water.

The stainless steel heat condensing body protects the main tank flow from corrosion and rusting enhancing performance and prolonging expected lifespan.

A powerful self-diagnostic system ensures everything inside is running on-point without the need for much by the way of maintenance.

You’ll get a remote control with the requisite cord included where much of the competition make you dig deeper for the privilege. The inbuilt blower and LED display lets you keep a close eye on temperature settings at a glance.

If you want to hook up 2 of these tankless heaters, the EZ-Link cable renders this a breeze.


  • Rock solid build as you’d expect from Rheem
  • Digital remote control and cord included to simplify operation
  • Works well at high altitudes up to 8400 feet


  • Expensive installation when venting is included

4) Rinnai RUC98iN Natural Gas Tankless Water Heater

While this Rinnai is substantial in terms of weight, you’ll get powerful performance to match.

You’ll be able to run this heater on natural gas or propane. You can also choose from the venting options listed below giving you a great deal of freedom.

The Rinnai can amply supply multiple bathrooms and faucets across a larger house with no interruption to supply. This is in large part due to a wide range of burn rate from 15,200 BTU right through to 199,000 BTU. Flow rate range is similarly wide maxing out at a full 9.8 Gallons Per Minute.

You can heat water from 95 to 140 Fahrenheit degrees.

Coming in ENERGY STAR certified, this natural gas tankless water heater has an EF rating of 0.96 giving the ability to shave precious dollars off your power bills while also reducing your environmental footprint.

As with all Rinnai water heaters, you’ll need to budget for professional installation which can also be tricky and time-consuming.


  • While weighing over 60 pounds, the Rinnai is sized like a suitcase so it’s a space-saver even if not especially lightweight
  • Twin venting options: concentric or twin-pipe PVC
  • Very wide span of flow rate from 0.26 GPM through an exceptional 9.8 GPM


  • Awkward to install and calls for professional assistance as well as possible tweaks to your home

5) Takagi T-H3-DV-N Condensing High-Efficiency Natural Gas Tankless Water Heater

Like all Takagi products, this tankless water heater is certainly not cheap but the best things in life seldom are.

Flow rate is 10 GPM and this unit is built to supply demanding hot water needs in sizeable properties.

Despite this hard-hitting performance, the heater itself is extremely compact.

As well as serving as a water heating device, you’ll also be able to use this heater with recirculation systems and radiant floor systems.

The copper-alloy heat exchanger tubing is built to stay the distance and the exchanger itself if guaranteed for 15 years while also ENERGY STAR certified.

Highly energy-efficient and with computerized safety features baked-in, you can enjoy on-demand hot water throughout your whole house from a powerful and quiet condensing water heater from a brand you can rely on.


  • Ultra-low NOx emissions meeting all relevant standards
  • Serves up to 4 bathrooms in warmer climates or 3 where the weather is colder
  • Condensing nature means this heater is extremely quiet in operation


  • You will use quite a high volume of natural gas and you’ll need specialized lines and components driving the price upward


Hopefully, you’ve found one of these condensing water heaters meets your needs.

Choosing an overall favorite is always tough but we make an assessment across all categories and do our best to oblige.

The Noritz NRC66DVNG gets our vote considering the ease of installation and price/performance ratio.

While it’s not cut out for servicing much larger homes, if you’ve got a regular house and you’re looking for a top-notch on-demand condensing tankless water heater, you can’t go wrong with this compact beast.

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