Hot Water List

RELIANCE WATER HEATERS ATHR-199M 1**

RELIANCE WATER HEATERS ATHR-199M 1** is in the DOE listing as of Oct 19, 2026. RELIANCE WATER HEATERS ATHR-199M 1** is in the ENERGY STAR list as of Oct 19, 2026.

  • Gas tankless water heater
  • 2 listed models

Its figures are also listed under A. O. Smith ATHR-199M 1**.

Certified and advertised figures

Flow at a 67°F rise
5.9gallons per minuteCertified
Advertised flow
5.9gallons per minuteRELIANCE WATER HEATERS, at a 67°F rise
UEF
0.95Uniform energy factor

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 5.6 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

RELIANCE WATER HEATERS ATHR-199M 1**: advertised and certified
RELIANCE WATER HEATERS ATHR-199M 1**: advertised and certified UEF: advertised 0.95, certified 0.95. Flow: advertised 5.9 gal/min, certified 5.9 gal/min (advertised at a 67°F rise, certified at a 67°F rise). UEF Advertised 0.95 Certified 0.95 Flow · advertised at a 67°F rise, certified at a 67°F rise Advertised 5.9 gal/min Certified 5.9 gal/min
RELIANCE WATER HEATERS ATHR-199M 1**: advertised figures, where and when read
FigureAdvertisedCertifiedAdvertiserRead
UEF 0.95 0.95 RELIANCE WATER HEATERS Read Oct 4, 2026
Flow 5.9 gal/min at a 67°F rise 5.9 gal/min at a 67°F rise RELIANCE WATER HEATERS Read Oct 4, 2026

See how advertised flow compares across tankless models

Certified figures by listed model

RELIANCE WATER HEATERS ATHR-199M 1**: certified figures by listed model
Model numberUEFFlow at a 67°F rise (gal/min)Recovery efficiencyDraw pattern
RTHR-199M 1**0.955.998%High
RTHR-199X3 1**0.955.998%High

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

ENERGY STAR certified models

RELIANCE WATER HEATERS ATHR-199M 1**: ENERGY STAR certified models
Model numberUEFFlow at a 67°F rise (gal/min)Recovery efficiency
RTHR-199M 1**0.955.998%
RTHR-199X3 1**0.955.998%

It heats 5.9 gallons per minute of water by 67°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 17 of the 487 gas tankless models.

All 2 of its model numbers are ENERGY STAR certified. In tests, 95% of the energy went to hot water, so its UEF is 0.95. Its test ran at the high level of daily hot water use. Among 399 gas tankless models on its draw pattern, 49 have a higher UEF. For its type and draw pattern, the UEF runs from 0.81 to 0.98. While it heats water, 98% of the energy used goes into the water (its recovery efficiency).

Its 2 model numbers are RTHR-199M 1** and RTHR-199X3 1**. All of its test figures are shared by 6 other basic models. Each of the 6 other brands lists one of them. You can find the whole group on the page for the A. O. Smith ATHR-199M 1**.

It may qualify for 6 rebate programs. Another 2 programs may accept it if it meets their other terms.

Also listed as

They carry every figure in the table above.

Rebates

Programs change their terms. Check the program's own page before you buy.

Updated Oct 19, 2026 · Methodology

Not covered

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