Editor’s note: Originally published December 2020. Reviewed and updated November 2026. Some models mentioned here may have been updated or discontinued since; check current availability and specifications before buying.
Takagi is a Japanese maker of gas tankless (on-demand) water heaters, with models for natural gas and liquid propane, indoor and outdoor mounting, and condensing or non-condensing designs. This guide compares three indoor natural gas models, from the compact T-KJr2 at 6.6 gallons per minute to the T-H3-DV-N at 10 gallons per minute, based on the manufacturer’s listed specifications.
Quick answer
- Smaller homes or radiant heating: Takagi T-KJr2-IN-NG, 140,000 BTU and 6.6 GPM.
- Average home with 2 to 3 bathrooms: Takagi T-K4-IN-NG, 190,000 BTU and 8 GPM.
- Larger homes with high demand: Takagi T-H3-DV-N, a condensing, direct-vent model with 199,000 BTU and 10 GPM.
- Takagi requires installation by a licensed professional for the warranty to be valid, and venting is sold separately.
Takagi indoor natural gas models compared
| Model | BTU | Flow rate | Weight | Dimensions (inches) | Best for |
|---|---|---|---|---|---|
| T-KJr2-IN-NG | 140,000 | 6.6 GPM | 38 lb | 6.7 x 13.8 x 20.3 | Smaller homes, radiant heating |
| T-K4-IN-NG | 190,000 | 8 GPM | 43 lb | 8.5 x 13.8 x 20.5 | 2 to 3 bathrooms |
| T-H3-DV-N | 199,000 | 10 GPM | 59 lb | 11.2 x 17.8 x 24.9 | Larger homes, high demand |
This guide covers only the indoor natural gas versions. The LP and outdoor versions work in much the same way internally; the differences are the fuel, mounting location and venting.
The Takagi models
Takagi T-KJr2-IN-NG
The T-KJr2 is Takagi’s smallest on-demand water heater. It delivers 6.6 gallons per minute from a compact, wall-mounted unit rated at 140,000 BTU. With no tank, it frees up floor space, and it suits radiant heating or smaller homes, which the original listing described as households of 3 to 5 people.
It comes with a detailed installation manual, but Takagi’s warranty is only valid if a licensed professional installs it. It’s also available as an outdoor model and in LP versions (T-KJr2-IN-LP indoor and T-KJr2-OS-LP outdoor).
Listed specifications
- Dimensions: 6.7 x 13.8 x 20.3 inches
- Weight: 38 pounds
- Fuel type: natural gas
- 140,000 BTU
- 6.6 gallons per minute
Pros
- Compact and efficient
- Wall-mounted to save space
- 120 V wired control panel for temperature adjustment and readouts
- Budget-friendly entry point to the range
- Detailed installation manual
Cons
- Warranty valid only with professional installation
- Exhaust venting sold separately
Takagi T-K4-IN-NG
The T-K4 replaced the older T-K3 and steps up to 8 gallons per minute and 190,000 BTU. That’s enough for the average home with 2 to 3 bathrooms, or roughly one more bathroom than the T-KJr2, and enough to run two showers at once. An outdoor version, the T-K4-OS-NG, is also available.
Listed specifications
- Dimensions: 8.5 x 13.8 x 20.5 inches
- Weight: 43 pounds
- Fuel type: natural gas
- 190,000 BTU
- 8 gallons per minute
Pros
- Continuous hot water, enough for two showers at once
- Compact and efficient
- Mid-range price for its output
Cons
- Real-world flow rate may fall slightly short of the listed figure
- Stainless steel exhaust vent sold separately
- Customer service has drawn complaints
- Warranty void if not installed by a licensed contractor
Takagi T-H3-DV-N
The T-H3-DV-N is the largest of the three, delivering 10 gallons per minute from 199,000 BTU of natural gas. It’s a condensing, direct-vent unit for indoor mounting only, with computerized safety features. Takagi rates it for four bathrooms in southern climates and three in northern climates, where incoming water is colder.
Listed specifications
- Dimensions: 11.2 x 17.8 x 24.9 inches
- Weight: 59 pounds
- Fuel type: natural gas
- 199,000 BTU
- 10 gallons per minute
- Condensing, direct vent, indoor only
Pros
- Highest output of the three
- 10 gallons per minute
- Condensing design
- Direct vent
Cons
- Can take several minutes for hot water to reach the faucet
- Reports of heat exchanger leaks
- Error codes may occur
Bottom line
Match the model to your hot water demand: the T-KJr2 for smaller homes, the T-K4 for a typical 2 to 3 bathroom house, and the T-H3-DV-N for larger homes or colder climates. Switching from a tank heater costs more up front, but tankless units save energy by heating water only when needed and can last longer than tank models. Read our tankless water heater pros and cons before deciding, and compare other brands in our Noritz NRC661-DV-NG and Rheem RTGH-95DVLN reviews.
FAQ
Can I install a Takagi tankless water heater myself?
Takagi requires installation by a licensed professional for the warranty to be valid, so professional installation is the safer choice.
Which Takagi model gives the most hot water?
Of the three covered here, the T-H3-DV-N, at 10 gallons per minute.
Are Takagi water heaters available for propane?
Yes. Takagi offers LP models as well as natural gas, for example the T-KJr2-IN-LP and T-KJr2-OS-LP.
