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Takagi TK-310U-I 2**

Takagi TK-310U-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-310U-I 2**.

Flow at a 67°F rise
4.7gallons per minuteCertified
Advertised flow
8.0gallons per minuteSupplyHouse, at a 35°F rise
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 4.5 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

Takagi TK-310U-I 2**: advertised and certified
Takagi TK-310U-I 2**: advertised and certified Flow: advertised 8.0 gal/min, certified 4.7 gal/min (advertised at a 35°F rise, certified at a 67°F rise). Flow: advertised 3.3 gal/min, certified 4.7 gal/min (advertised at a 70°F rise, certified at a 67°F rise). Flow: advertised 7.9 gal/min, certified 4.7 gal/min (advertised at a 40°F rise, certified at a 67°F rise). Flow: advertised 6.2 gal/min, certified 4.7 gal/min (advertised at a 50°F rise, certified at a 67°F rise). Flow · advertised at a 35°F rise, certified at a 67°F rise Advertised 8.0 gal/min Certified 4.7 gal/min Flow · advertised at a 70°F rise, certified at a 67°F rise Advertised 3.3 gal/min Certified 4.7 gal/min Flow · advertised at a 40°F rise, certified at a 67°F rise Advertised 7.9 gal/min Certified 4.7 gal/min Flow · advertised at a 50°F rise, certified at a 67°F rise Advertised 6.2 gal/min Certified 4.7 gal/min
FigureAdvertisedCertifiedAdvertiserRead
Flow 8.0 gal/min at a 35°F rise 4.7 gal/min at a 67°F rise SupplyHouse Archived copy, Apr 18, 2025
Flow 3.3 gal/min at a 70°F rise 4.7 gal/min at a 67°F rise SupplyHouse Archived copy, Apr 18, 2025
Flow 7.9 gal/min at a 40°F rise 4.7 gal/min at a 67°F rise SupplyHouse Archived copy, Apr 18, 2025
Flow 6.2 gal/min at a 50°F rise 4.7 gal/min at a 67°F rise SupplyHouse Archived copy, Apr 18, 2025
Flow 5.3 gal/min at a 60°F rise 4.7 gal/min at a 67°F rise SupplyHouse Archived copy, Apr 18, 2025
Flow 4.5 gal/min at a 70°F rise 4.7 gal/min at a 67°F rise SupplyHouse Archived copy, Apr 18, 2025

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
TK-310U-I 2**0.814.784%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 4.7 gallons per minute. The gas tankless type has a median flow of 4.8 gallons per minute. Of 487 gas tankless models, 252 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). The daily hot water use in the test, called its draw pattern, was high. Its UEF is lower than that of 327 of the 399 gas tankless models with its draw pattern. A UEF of 0.93 is the median for its type and draw pattern. Of the energy it spends heating water, 84% ends up in it (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-I 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.