State TK-310U-E 2**
State TK-310U-E 2** is in the DOE listing as of Oct 19, 2026.
- Gas tankless water heater
- 1 listed model
Not listed as ENERGY STAR certified on Oct 19, 2026.
Its figures are also listed under A. O. Smith TK-310U-E 2**.
Certified figures
- Flow at a 67°F rise
- 4.8gallons per minute
- UEF
- 0.81Uniform energy factor
Your fixtures at once
Change your hour and flowFlow where you live
The heater gives less flow when colder incoming water needs a bigger rise.
- Cold water
- Cold water must be at least 10°F colder than the hot water setting.
- Flow estimate
- The estimate uses the lowest certified flow among the listed models. It is about 4.6 gal/min at a 70°F rise.
Flow limits
- The estimate excludes the flow needed to turn the heater on, heat lost in pipes, and installation.
- Cold water from a well or long pipe run can differ from the temperature you enter.
- Without a stated flow limit, estimates for warmer water may exceed the heater’s actual flow.
Certified figures by listed model
| Model number | UEF | Flow at a 67°F rise (gal/min) | Recovery efficiency | Draw pattern |
|---|---|---|---|---|
| GTS-310U-E 2** | 0.81 | 4.8 | 86% | High |
UEF is the uniform energy factor. A dash means the model has no such figure.
At a 67°F rise, its flow in the test is 4.8 gallons per minute. The gas tankless type has a median flow of 4.8 gallons per minute. Of 487 gas tankless models, 221 have a higher flow than this one.
It was not listed as ENERGY STAR certified on Oct 19, 2026. In tests, 81% of the energy it uses ends up as hot water (UEF 0.81). Its test ran at the high level of daily hot water use. Of 399 gas tankless models with the same draw pattern, 327 have a higher UEF. A UEF of 0.93 is the median for its type and draw pattern. When it runs, 86% of the energy it uses reaches the water (its recovery efficiency).
All of its test figures are shared by 5 other basic models. Each of the 5 other brands lists one of them. For the full group, see the A. O. Smith TK-310U-E 2**.
Also listed as
They carry every figure in the table above.
- Every State basic model
- Every gas tankless water heater certified at 4.0 to 4.9 gallons per minute
- Every gas tankless water heater
- The most-searched gas tankless models side by side
Not covered
- Advertised figures. We have none on file for this model.