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Lochinvar TK-310U-E 2**

Lochinvar 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**.

Flow at a 67°F rise
4.8gallons per minuteCertified
Advertised flow
8.0gallons per minuteLochinvar, up to, no rise stated
UEF
0.81Uniform energy factor
See it among every gas tankless model

Flow 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.

Advertised and certified figures

Lochinvar TK-310U-E 2**: advertised and certified
Lochinvar TK-310U-E 2**: advertised and certified UEF: advertised 0.81, certified 0.81. UEF: advertised 0.81, certified 0.81 (advertised up to). Flow: advertised 8.0 gal/min, certified 4.8 gal/min (advertised up to, no rise stated, certified at a 67°F rise). Flow: advertised 4.8 gal/min, certified 4.8 gal/min (advertised at a 67°F rise, certified at a 67°F rise). UEF Advertised 0.81 Certified 0.81 UEF · advertised up to Advertised 0.81 Certified 0.81 Flow · advertised up to, no rise stated, certified at a 67°F rise Advertised 8.0 gal/min Certified 4.8 gal/min Flow · advertised at a 67°F rise, certified at a 67°F rise Advertised 4.8 gal/min Certified 4.8 gal/min
FigureAdvertisedCertifiedAdvertiserRead
UEF 0.81 0.81 Lochinvar Read Oct 4, 2026
UEF up to 0.81 0.81 Lochinvar Read Oct 4, 2026
Flow up to 8.0 gal/min, no rise stated 4.8 gal/min at a 67°F rise Lochinvar Read Oct 4, 2026
Flow 4.8 gal/min at a 67°F rise 4.8 gal/min at a 67°F rise Lochinvar Read Oct 4, 2026

See how advertised flow compares across tankless models

Certified figures by listed model

Model numberUEFFlow at a 67°F rise (gal/min)Recovery efficiencyDraw pattern
LTO-310U 2**0.814.886%High

UEF is the uniform energy factor. A dash means the model has no such figure.

It warms 4.8 gallons per minute of water from 58°F to 125°F in the test. The median flow among gas tankless models is 4.8 gallons per minute. Its flow at a 67°F rise trails 221 of the 487 gas tankless models.

As of Oct 19, 2026, it was not listed as ENERGY STAR certified. In the test, 19% of its energy does not reach the hot water (UEF 0.81). In the test, daily hot water use was set to high (its draw pattern). Among 399 gas tankless models on its draw pattern, 327 have a higher UEF. A UEF of 0.93 is the median for its type and draw pattern. While it heats water, 86% of the energy used goes into the water (its recovery efficiency).

There are 5 more basic models with the same test figures. Each of them is listed under a different brand. You can find the whole group on the page for the A. O. Smith TK-310U-E 2**.

Also listed as

They carry every figure in the table above.

Updated Oct 19, 2026 · Methodology

Not covered

  • Changes to an advertised figure after the date beside it.