Tankless Water Heaters are typically selected based on the amount of hot water they are able to produce.
If selecting a Takagi water heater strictly for hot water heating applications, you need to determine the maximum amount of plumbing fixtures that you will be running at the same time. Shower, for example, is considered to be a basic plumbing fixture.
The chart below represents typical outputs (number of showers or other appliances, such as a dishwasher, washer) of various Takagi tankless water heater models based on the incoming ground water temperatures. The warmer the ground temperature is, the more hot water the unit will produce:
| MODEL | WARMER CLIMATES (70°F Incoming Groundwater Temperature) |
COLDER CLIMATES (40°F Incoming Groundwater Temperature) |
|---|---|---|
| T-K Jr2-IN/OS | 2 | 1 |
| T-K4-IN/OS | 3 | 2 |
| T-H2-DV/OS | 4 | 3 |
| Model | BTU Max (NG) |
BTU Min (NG) |
Flow Rating (DOE) |
First Hour Rating (DOE) |
Net Weight (lbs) |
Efficency | Dimension (in.) |
|---|---|---|---|---|---|---|---|
| T-K Jr2-IN/OS | 140,000 BTU |
19,500 BTU |
6.8 GPM |
228 gallons/hour 3.3 gallons/minute (70°F rising) |
33 lbs | NG 0.82 LP 0.83 |
20.5" (H) 13.8" (w) 6.7" (D) |
| T-K4-IN/OS | 190,000 BTU |
11,000 BTU |
8.0 GPM |
264 gallons/hour 4.4 gallons/minute (70°F rising) |
38 lbs | NG 0.82 LP 0.82 |
20.5" (H) 13.8" (W) 8.5" (D) |
| T-H2-DV/OS | 199,000 BTU |
13,000 BTU |
9.0 GPM |
312 gallons/hour 5.2 gallons/minute (70°F rising) |
73 lbs | NG 0.91 LP 0.91 |
20.5" (H) 13.8" (W) 8.5" (D) |
| T-D2-IN/OS | 199,000 BTU |
11,000 BTU |
10.0 GPM |
282 gallons/hour 4.7 gallons/minute (70°F rising) |
39 lbs | NG 0.82 LP 0.82 |
20.5" (H) 13.8" (W) 8.5" (D) |
| T-M32 | 240,000 BTU |
24,000 BTU |
9.0 GPM |
299 gallons/hour 5.0 gallons/minute (70°F rising) |
59 lbs | NG 82.2% LP 83.9% |
23.6" (H) 18.5" (W) 8.9" (D) |
| T-M50 |
380,000 BTU |
15,000 BTU |
14.5 GPM |
474 gallons/hour 7.9 gallons/minute (70°F rising) |
102 lbs | NG 80.2% LP 82.4% |
25.3" (H) 24.8" (W) 11.8" (D) |
For outdoor installations, the Takagi T-K4-OS is the best, especially for warmer climates. It is designed to be installed without any venting parts, thus eliminating any additional costs and significantly cutting the installation time. This model can output as much as 480 gallons of hot water per hour.
For 1 bathroom + 1 kitchen applications, Takagi T-KJr2 (a.k.a Takagi t-KJr2) model is the optimal choice. It is very cost efficient and offers a variety of installation options, both indoors and outdoors. This model is capable of producing as much as 396 gallons of hot water per hour.
Takagi T-K4 is the most versatile unit and one of the most popular in the Takagi line of water heaters. It is packed with features, with the most outstanding being the Easy-Link technology, which allows you to connect up to (3) Takagi T-K4 units in series without the use of any additional equipment. This option is particularly useful when there’s a chance of under-sizing the unit, or if the system will be extended in the future. A single T-K4 model can produce up to 480 gallons of hot water per our. 3 units together can output as much as 1440 gallons.
When sizing a Takagi tankless water heater for hydronic or radiant heating applications, it is also important to consider the maximum flow rate, as it is directly linked to the amount of heat in BTU’s the unit can produce. Since most of the hydronic and radiant heating systems operate at equation 1 GPM = 10,000 BTU’s, knowing the GPM will tell you the heat output of the unit.