A. O. Smith TK-510U-I 2**
A. O. Smith TK-510U-I 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-510U-E 2**.
Certified and advertised figures
- Flow at a 67°F rise
- 5.0gallons per minuteCertified
- Advertised flow
- 10.0gallons per minuteA. O. Smith, up to, no rise stated
- UEF
- 0.81Uniform energy factor
Your fixtures at once
Change your hour and flowFlow where you live
A bigger rise from colder incoming water leaves the heater with 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 4.8 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 | A. O. Smith | Read Oct 5, 2026 |
| UEF | up to 0.81 | 0.81 | A. O. Smith | Read Oct 5, 2026 |
| Flow | up to 10.0 gal/min, no rise stated | 5.0 gal/min at a 67°F rise | A. O. Smith | Read Oct 5, 2026 |
| Flow | 5.0 gal/min at a 67°F rise | 5.0 gal/min at a 67°F rise | A. O. Smith | Read Oct 5, 2026 |
Certified figures by listed model
| Model number | UEF | Flow at a 67°F rise (gal/min) | Recovery efficiency | Draw pattern |
|---|---|---|---|---|
| ATI-510U 2** | 0.81 | 5.0 | 84% | High |
UEF is the uniform energy factor. A dash means the model has no such figure.
It heats 5.0 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, 176 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). Of 399 gas tankless models with the same draw pattern, 327 have a higher UEF. For its type and draw pattern, the UEF runs from 0.81 to 0.98. While it heats water, 84% of the energy used goes into the water (its recovery efficiency).
All of its test figures are shared by 13 other basic models. Between them, those basic models carry 6 other brand names. You can find the whole group on the page for the A. O. Smith TK-510U-E 2**.
Also listed as
They carry every figure in the table above.
- A. O. Smith TK-510U-E 2**
- American TK-510U-E 2**
- American TK-510U-I 2**
- Lochinvar TK-510U-E 2**
- Lochinvar TK-510U-I 2**
- Navien NHW700-199AE-NG
- Navien NHW700-199AI-NG
- RELIANCE WATER HEATERS TK-510U-E 2**
- RELIANCE WATER HEATERS TK-510U-I 2**
- State TK-510U-E 2**
- State TK-510U-I 2**
- Takagi TK-510U-E 2**
1 more basic model carry these figures.
- Every A. O. Smith basic model
- Every gas tankless water heater certified at 5.0 to 5.9 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.