Heating water accounts for a massive chunk of your utility bill. If you want to stop throwing money down the drain, switching to a condensing water heater is one of the smartest upgrades you can make.
While traditional heaters vent hot exhaust gas outside, condensing units capture that heat and recycle it to warm incoming water. The result? Incredible efficiency and lower monthly costs.
We analyzed the market to find the top performers. We looked for units that offer high flow rates for busy families, compact designs for tight spaces, and the best overall value for your budget.
- High flow rate at 10 GPM
- Emits low amounts of NOx
- User-friendly digital interface
- Weighs just 39 lbs
- Remote controlled thermostat
- 12-year warranty
- Can be installed horizontally or vertically
- Fully automatic
- Works with low water pressure (8 psi)
How Do Condensing Water Heaters Work?
Standard tankless water heaters burn gas to heat water, sending the hot exhaust gases immediately out of a vent. That exhaust is essentially wasted energy.
Condensing water heaters use a second heat exchanger to capture that exhaust gas before it escapes. They use the residual heat to pre-warm the cold water entering the system. By the time the exhaust vents, it is much cooler, and the water is already partially heated.
This process squeezes every ounce of energy from the fuel. These units typically boast a Uniform Energy Factor (UEF) of 0.90 or higher, meaning 90 percent (or more) of the fuel is converted directly into hot water.
Things to Consider
Before you invest in a new system, here are the critical factors that should drive your decision.
Tank vs. Tankless
While most condensing technology is found in tankless units, it helps to understand the distinction if you are transitioning from an older system.
Tank
Traditional tank heaters store 40 to 50 gallons of hot water 24/7. They are generally cheaper upfront and simpler to install. However, they suffer from “standby loss” because they constantly burn fuel to keep the water hot, even when you aren’t home.
We did not include any standard tank units in this list because condensing technology has largely shifted toward tankless designs for maximum efficiency.
Pros
- Lower upfront cost.
Cons
- Limited hot water supply.
- Higher energy bills due to standby heat loss.
Tankless
Tankless units heat water on demand. When you open a tap, the burners ignite and heat the water as it flows through the exchanger. This offers an endless supply of hot water, provided you don’t exceed the flow rate capacity.
Because they don’t store hot water, they are significantly more efficient. The initial price tag is higher, but the long-term savings on gas bills often make up for it.
Pros
- Endless hot water supply.
- Compact, wall-mounted design saves floor space.
- Significant energy savings.
Cons
- Higher initial purchase price.
- May require venting upgrades.
Digital vs. Remote Interface
Controlling your water temperature shouldn’t be a hassle. Manufacturers generally offer two ways to interact with the unit.
Integrated Digital Panel
Many units have a control panel built directly onto the front casing. This is straightforward and reliable. However, if your heater is installed in a crawl space, attic, or basement, making adjustments can be inconvenient.
Pros
- Simple and durable.
- No wiring for external controllers required.
Cons
- Inconvenient if the unit is installed in a hard-to-reach area.
Remote Thermostat
Some models come with (or support) remote controllers. These can be mounted in a bathroom, laundry room, or kitchen. This allows you to adjust the output temperature without trekking to the utility room.
Pros
- Adjust temperature from the comfort of your living space.
- Great for prioritizing hotter water for laundry or dishwashers.
Cons
- Requires running wire from the unit to the controller location.
Venting Materials
This is a major installation advantage of condensing units. Because the secondary heat exchanger pulls so much heat out of the exhaust, the gas that vents outside is relatively cool.
Traditional heaters require expensive stainless steel venting to handle high heat. Condensing heaters can often use inexpensive PVC or CPVC piping for venting. This can save you hundreds of dollars on installation materials.
Flow Rate (GPM)
Gallons Per Minute (GPM) determines how many fixtures you can run simultaneously. If you try to run two showers and a dishwasher on a unit with low GPM, you will experience a drop in pressure or temperature.
- Bathroom Faucet: 0.5 to 1.5 GPM.
- Shower: 2.0 to 3.0 GPM.
- Kitchen Faucet: 1.5 to 2.5 GPM.
For a family of four with two bathrooms, look for a unit that delivers at least 8 to 10 GPM to ensure peak-hour comfort.
Product Reviews
We evaluated these units based on efficiency ratings, flow rate capacity, build quality, and ease of installation.
Takagi T-H3-DV-N Condensing Tankless Water Heater
Highest Flow Rate
The Takagi T-H3 is a powerhouse designed for heavy usage. If you have a busy household where multiple people shower at the same time while the laundry is running, this is the unit you want.
It utilizes commercial-grade copper alloy for the primary heat exchanger and durable stainless steel for the secondary condensing exchanger. This combination ensures efficient heat transfer and long-term durability against corrosion.
What We Like
Massive GPM Capacity
With a max flow rate of 10 GPM, this unit is a beast. In warmer climates, it can easily handle four showers simultaneously. Even in colder northern climates, it maintains enough flow for two simultaneous showers plus an appliance. It eliminates the morning traffic jam in the bathroom.
Smart Safety Features
Takagi includes computerized safety features that you don’t always see on budget models. It has internal freeze protection, overheat cutoff fuses, and constant temperature monitoring. This gives you peace of mind that the unit will protect itself (and your home) if something goes wrong.
Compact Yet Powerful
Despite its high output, the unit weighs only 59 pounds and is small enough to mount on almost any wall. It frees up valuable floor space compared to the massive tank heaters it usually replaces.
What We Don't Like
Professional Installation Recommended
While the venting is flexible, the gas line requirements are strict. You need to ensure your gas supply line is sized correctly to handle the BTU input, otherwise, the unit will throw error codes.
Product Specs
| Dimensions | 11.2 x 17.8 x 24.9 inches |
| Weight | 85 pounds |
| Flow Rate (Gallons Per Minute) | 10 GPM |
| Input Type | Gas operated |
| Digital or Remote? | Digital |
| Indoor or Outdoor Use? | Indoor only |
Our Ratings
Noritz NRC66DVNG Indoor Condensing Tankless Water Heater
Smallest Condensing Water Heater
Noritz creates units that focus on reliability and ease of retrofitting. The NRC66 is specifically designed for smaller homes, apartments, or condos where space is a luxury.
It features dual stainless steel heat exchangers, which are highly resistant to corrosion and scale buildup. If you are looking to replace a 40-gallon tank heater with something that takes up zero floor space, this is a solid contender.
What We Like
Ultra-Compact Design
This unit is incredibly unobtrusive. You can install it in a closet, a small utility room, or even under a staircase. The white finish is clean and modern, so it doesn’t look like an industrial eyesore if it happens to be visible.
Remote Included
Unlike some competitors that make you buy the controller separately, Noritz includes a remote thermostat. You can mount this in your kitchen or bathroom to easily adjust the temperature or view error codes without accessing the unit itself.
Lower Activation Flow
This unit activates at a flow rate of just 0.5 GPM. This means you don’t have to turn the faucet on full blast just to trigger the hot water, which is great for shaving or light washing.
What We Don't Like
Lower Total Capacity
This unit tops out at around 6.6 GPM. While that is plenty for a 1-2 bathroom home, it will struggle in a larger house with high demand. It is strictly a residential solution for smaller families or couples.
Product Specs
| Dimensions | 6.7 x 13.8 x 23.6 inches |
| Weight | 39 pounds |
| Flow Rate (Gallons Per Minute) | 6.5 GPM |
| Input Type | Gas operated |
| Digital or Remote? | Remote |
| Indoor or Outdoor Use? | Indoor |
Our Ratings
Rinnai RUR98iN Ultra Series Tankless Water Heater
Most Aesthetically Pleasing
Rinnai is arguably the most recognized name in the tankless game, and the Ultra Series shows why. This unit isn’t just about heating water; it’s about delivering it faster.
It features internal recirculation capability (with the addition of a pump kit on some setups), which helps eliminate the cold water sandwich effect. The sleek silver finish looks premium, and the internal components are built to last.
What We Like
Recirculation Ready
Waiting for hot water to travel from the heater to your shower wastes gallons of water. The Rinnai is designed to work with recirculation systems to keep hot water available at the tap instantly. This adds a layer of luxury and convenience that standard tankless units lack.
Concentric Venting
This unit uses concentric venting, which pulls fresh air in and pushes exhaust out through a single pipe penetration. This makes installation cleaner and requires fewer holes in your siding or roof.
High Efficiency
With a 0.96 Energy Factor, this is one of the most efficient gas appliances you can buy. It wastes almost nothing, ensuring your gas bill stays as low as possible.
What We Don't Like
Heavy Unit
Build quality comes with weight. This unit is heavier than the Noritz or Takagi models, so you need to ensure your wall mounting location has proper blocking or stud support.
Product Specs
| Dimensions | 12.5 x 10 x 26 inches |
| Weight | 81.6 pounds |
| Flow Rate (Gallons Per Minute) | 9.8 GPM |
| Input Type | Gas operated |
| Digital or Remote? | Remote |
| Indoor or Outdoor Use? | Indoor only |
Our Ratings
EZ Ultra HE Condensing Tankless Water Heater
Most Efficient Condensing Water Heater
The EZ Ultra HE is designed for the budget-conscious homeowner who doesn’t want to sacrifice condensing efficiency. It offers a very attractive price point while still delivering the energy savings of a condensing unit.
It is particularly popular for DIY-friendly installations (though we always recommend a pro for gas lines) because of its straightforward connections and flexible venting options.
What We Like
Exhaust Gas utilization
This unit excels at capturing latent heat. By utilizing the exhaust gas so effectively, it ensures that the unit runs cooler and uses less propane or natural gas than non-condensing competitors.
Simple Venting
You can run a single 2-inch PVC pipe for the exhaust. This is cheap, easy to cut, and easy to source at any local hardware store. It simplifies the most intimidating part of the installation process.
Low Pressure Operation
It can ignite with very low water pressure (as low as 8 PSI). If you live in a rural area with a well pump or have older plumbing with inconsistent pressure, this heater is forgiving and reliable.
What We Don't Like
Slow Ignition Time
Users note that it can take a few seconds longer to fire up and deliver hot water compared to the premium Takagi or Rinnai models. It’s not a dealbreaker, but it is noticeable if you are used to instant systems.
Product Specs
| Dimensions | 27 x 14.5 x 6.5 inches |
| Weight | 31 pounds |
| Flow Rate (Gallons Per Minute) | 3.4 GPM |
| Input Type | Gas operated |
| Digital or Remote? | Digital |
| Indoor or Outdoor Use? | Indoor |
Our Ratings
| Product | Award | Dimensions | Weight | Flow Rate | Input Type | Digital/ Remote | Indoor/ Outdoor |
|---|---|---|---|---|---|---|---|
| Takagi T-H3-DV-N | Highest Flow Rate | 11.2″ x 17.8″ x 24.9″ | 85 lbs | 10 GPM | Gas | Digital | Indoor |
| Noritz NRC66DVNG | Smallest Heater | 6.7″ x 13.8″ x 23.6″ | 39 lbs | 6.5 GPM | Gas | Remote | Indoor |
| Rinnai RUR98iN | Most Aesthetically Pleasing | 12.5″ x 10″ x 26″ | 81.6 lbs | 9.8 GPM | Gas | Remote | Indoor |
| EZ Ultra HE | Most Efficient | 27″ x 14.5″ x 6.5″ | 31 lbs | 3.4 GPM | Gas | Digital | Indoor |
FAQs
What Is the Difference Between Condensing and Non-Condensing?
The main difference is efficiency and venting. Non-condensing units vent hot exhaust gas (around 300°F) immediately, requiring metal venting. Condensing units capture that heat to pre-warm the water, lowering the exhaust temperature significantly (around 100°F) and allowing the use of cheaper PVC venting.
What Is a Condensing Water Heater?
A condensing water heater is a high-efficiency unit that recycles waste heat. Instead of letting hot exhaust gases escape, it passes them through a secondary heat exchanger. This transfers the heat to the incoming cold water, increasing efficiency to over 90 percent and reducing fuel consumption.
Are Condensing Water Heaters More Efficient?
Yes, they are significantly more efficient. While standard tankless heaters operate at about 80 percent efficiency, condensing models reach between 93 and 98 percent efficiency. This means for every dollar you spend on gas, nearly the entire dollar goes toward heating your water rather than heating the air outside your house.
Are Condensing Water Heaters Tankless?
Most residential condensing water heaters are tankless, but hybrid models do exist. Manufacturers focus on tankless designs for condensing technology because the on-demand nature of the system pairs perfectly with the high-efficiency heat exchangers to maximize energy savings.
Are Condensing Water Heaters Worth the Extra Cost?
If you plan to stay in your home for several years, they are absolutely worth it. The upfront cost is higher, but the installation is often cheaper due to PVC venting, and the monthly gas savings are substantial. Additionally, many utility companies offer rebates for installing high-efficiency condensing units.
Does a Condensing Tankless Water Heater Need a Drain?
Yes, it requires a condensate drain. The process of pulling heat from exhaust gas creates acidic water (condensation). This liquid must be drained away. You will need a neutralizer kit (a small box filled with limestone chips) to treat the acidic water before it flows into your home’s drain system.
How Much Do They Cost?
You can expect to pay between $1,000 and $2,500 for the unit itself, depending on the GPM capacity and brand. Installation costs vary widely but generally range from $500 to $1,500, depending on whether you need new gas lines or electrical outlets installed.
Is Installation Difficult?
Installation is complex and usually requires a licensed professional. You are dealing with gas lines, high-voltage electricity, and water plumbing simultaneously. Incorrect installation can lead to gas leaks, carbon monoxide issues, or voiding the manufacturer’s warranty.
