American TK-310U-E 2**
American 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 and advertised figures
- Flow at a 67°F rise
- 4.8gallons per minuteCertified
- Advertised flow
- 10.0gallons per minuteAmerican, up to, no rise stated
- UEF
- 0.81Uniform energy factor
Your fixtures at once
Change your hour and flowFlow where you live
Colder incoming water needs a bigger rise, so the heater gives less flow.
- 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.
Advertised and certified figures
| Figure | Advertised | Certified | Advertiser | Read |
|---|---|---|---|---|
| UEF | 0.81 | 0.81 | American | Read Oct 4, 2026 |
| Flow | up to 10.0 gal/min, no rise stated | 4.8 gal/min at a 67°F rise | American | Read Oct 4, 2026 |
| Flow | 4.8 gal/min at a 67°F rise | 4.8 gal/min at a 67°F rise | American | Read Oct 4, 2026 |
Certified figures by listed model
| Model number | UEF | Flow at a 67°F rise (gal/min) | Recovery efficiency | Draw pattern |
|---|---|---|---|---|
| GT-310U-E 2** | 0.81 | 4.8 | 86% | High |
UEF is the uniform energy factor. A dash means the model has no such figure.
It heats 4.8 gallons per minute of water by 67°F in the test. The median gas tankless model heats 4.8 gallons per minute by 67°F. Of 487 gas tankless models, 221 have a higher flow than this one.
As of Oct 19, 2026, it was not listed as ENERGY STAR certified. In tests, 81% of the energy it uses ends up as hot water (UEF 0.81). Its test simulated a day of high hot water use (its draw pattern). Among 399 gas tankless models on its draw pattern, 327 have a higher UEF. For its type and draw pattern, the UEF runs from 0.81 to 0.98. When it runs, 86% of the energy it uses reaches the water (its recovery efficiency).
Its test figures match those of 5 other basic models. They are listed under 5 other brands, one each. For the full group, see the A. O. Smith TK-310U-E 2** page.
Also listed as
They carry every figure in the table above.
- Every American 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
- Changes to an advertised figure after the date beside it.