Takagi T-H3-DV Gas Tankless Water Heater

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Editor’s Conclusion
If you are a homeowner in need of a new hot water tank, going tankless can be the way to go if you want to save energy over the long run. If you already have a gas line to your home, you might consider a tankless gas water heater. While gas tankless units are pricey to buy and install, they are long-lasting and reliable, and they can even overcome some of the limitations of electric tankless units. Tankless electric owners often complain that their heater fails to deliver the hot water needed when multiple family members are taking a shower, running a load of clothes, or washing their hands.

The Takagi T-H3-DV is one of the smallest tankless gas water units in its range yet is considered one of the best energy-saving water heaters with an energy factor of 0.95 and hot water output of 10 gallons per minute (GPM). Most gas tankless heaters have about a .85 efficiency rating – much less than electric tankless heaters that have .98 or more as most of the energy is used to heat the water. This Takagi, with its condensation system, comes closer to the electric tankless numbers than most gas units do.

The large capacity means that this tankless gas hot water heater does what it is supposed to – supply hot water to a sizable household. In warmer climates, this Takagi water heater reaches its full potential, but even when the inlet water is not warm enough to deliver the promised 10 gallons of hot water, the output still exceeds what many electric units can deliver.
Takagi T-H3-DV Gas Tankless Water Heater Review Facts
Editor's Pros & Cons

Endless hot water with 10 GPM delivery for on-demand usage

Compact, space-saving design

No pilot light to waste energy

Computerized safety features include freeze, overheat, surge protection, and troubleshooting diagnostic codes

Satisfies the 2012 SCAQMD Rule 1146.2 for Ultra-Low NOx Emissions

Primary heat exchanger utilizes commercial-grade copper alloy for 25 times better heat transfer than stainless steel

Integrated controls and power cord as standard features


Expensive to buy and install

Slight delay in providing first warm water

Requires a special venting and pipe system and professional installation

As with most tankless units, GPM drops in cooler climates.

Key Features

Capable of producing 10 gallons of 100°-185° hot water per minute, the Takagi T-H3-DV-N is an indoor condensing gas-fired tankless water heater with high energy and thermal efficiency. Its output makes it perfect for medium to large households where there are multiple simultaneous needs for water.

With a gas output of up to 199,000 BTUs, the unit can quietly service four bathrooms, faucets, or washers with endless hot water in warmer climates or three in cooler climates where the inlet water temperature is lower. The assumption is that usage will be mixed; four people showering at the same time would tax any unity, but the Takagi might easier handle a shower while the dishwasher is running, and others are washing their hands.

Notable Features

The Takagi T-H3-DV has a compact space-saving design, which at 10.75” x 17.75” x 22.5” requires much less space than a tank and fits in small spaces. This model features an LED screen with illuminated buttons for setting the temperature.

Made in Japan, this unit uses the best of Japanese and American water heater technology to make it long-lasting and durable. The manufacturer has such confidence in how the Takagi T-H3-DV performs and lasts that it offers a 15-year limited warranty on units used for domestic purposes or 10 years in a commercial setting. Both residential and commercial projects have a five-year limited warranty on parts or a one-year additional warranty on labor and a six-year warranty on the heat exchanger. This water heater will probably last two decades or more.

This water heater can also be installed as part of a home heating system. In this case, a heating and ventilation contractor should install it.


The high-efficiency rate of .95 is due to its being a condensation unit, which uses a secondary heat exchanger to take the exhaust from a regular 80% efficient main heat exchanger, cool down the exhaust so that it changes from steam to water, and "work" the water again to heat it even more. Reusing the exhaust adds 15%-17% to the efficiency rate. The exhaust is cool enough that it condensates, runs down a vent into a tray, and then goes down a PVC condensation drain.

The primary heat exchanger utilizes commercial-grade copper alloy for 25 times better heat transfer than stainless steel, while the secondary heat exchanger utilizes 316L stainless steel for better corrosion resistance.

The efficiency also results from energy-saving features as a self-modulating heating mechanism, surge protection, diagnostics codes, and anti-freeze and overheating protection that also cuts your water-heating bills. The unit also has an extremely low nitrogen oxide emission rate so little gas escapes into your home, and the carbon footprint is minimal.

While condensing units, such as the Takagi T-H3-DV-N, priced at $1,139 on Amazon are more costly than non-condensing models to buy, operating costs are lower, and performance, measured in higher first-hour ratings and recovery rates, are higher.


Installation and maintenance of a gas hot water system can seldom be handled by a homeowner, due to the venting and piping system required.

To ensure safe fuel combustion and performance, gas tankless heaters should be inspected annually by a trained technician. Gas tankless water heaters have extremely complex heat exchangers and fuel controls that require expertise to examine and service.

Comparison to Others

The Takagi T-H3-DV-N7 has other competitors in the gas hot water tank market such as Rinnai, Rheem, Noritz, Eccotemp, Bosch, and even other Takagi models, but only the Bosch 940 ES NG Indoor Natural Gas Tankless Water Heater offers an energy efficiency factor of .95 to compete with this model. The Noritz NRC661-DV-NG comes close at .89, but most other top models hover in the low 80s.

The product has 65% 5-star ratings and 14% 4-star ratings on Amazon, which seems low, considering how highly praised this water heater is in reviews. Although this model has been available since 2013, there are only 165 Amazon reviews, which may mean that Amazon did not carry the product for part of the time. Many of the low ratings came due to disappointing vendors, installation problems, and performance issues that may relate to having a cooler climate in the part of the country where the customer resides.

Our Verdict

The T-H3-DV-N7 by Takagi has a lot to offer in energy efficiency, performance, longevity, and reliability. Anyone with a gas line available who is willing to invest in the purchase and installation costs of this tankless gas hot water heater should be well pleased.