RELIANCE WATER HEATERS T-H3M-OS-N 1**
0.91 UEF DOE CCD · 2026-09-19Grade C: where this UEF sits among the 80 models in its class, lowest (G) to highest (A). A position, not an official label. How the grade is set
A gas tankless unit, medium draw pattern (a typical three- or four-person household, about 55 gallons on a busy morning).
If you are verifying this unit, RELIANCE WATER HEATERS T-H3M-OS-N 1** uses 122 therms of natural gas a year at the medium draw pattern. A draw pattern is the standard daily hot-water usage DOE tests against. That is 13 therms below the class median of 135 therms, and it ranks 4th lowest for energy use of 80 gas tankless models.
Energy use per year
122 therms a year
Computed by this site from the registry's UEF and the federal test's daily hot-water draw for this draw pattern. What it costs depends on the natural gas rate where you live.
That is below the median of 135 therms for the 80 models registered in the same heater type and draw pattern; it ranks 4 of 80, lowest energy first.
Solid line: this model (122 therms). Dashed line: the class median.
Min 114 therms Median 135 therms Max 137 therms
What it costs to run where you live
What the registry files
- UEF (Uniform Energy Factor) how much hot water you get for each unit of energy the heater uses
- 0.91 DOE CCD · 2026-09-19 Compared only with other models registered as a gas tankless unit at the medium draw pattern.
- Draw Pattern the standard daily usage profile DOE tests the unit against
- Medium DOE CCD · 2026-09-19
- Maximum Gallons Per Minute how many gallons a minute it can heat while running continuously
- 3.5 gal/min DOE CCD · 2026-09-19
What it costs to install
$2,169–$3,184 installed
Not a quote — a modeled range of what installers have charged for this class of unit; your price will vary with labor rates, access, and local code requirements.
Escalation indexes: equipment (BLS PPI) latest available: August 2026; labor (BLS ECI) latest available: April 2026 to June 2026.
NLR REMDB (BLS PPI/ECI escalated) · 2026-04-01Safety record
No CPSC recall names this model.
Checked against the CPSC recall database. CPSC does not publish a model-level match for this product category, so this list is curated by hand from the manufacturer's recall filings.
CPSC · 2026-09-24What these figures mean
How this compares
The closest models in the same class — same fuel, type and draw pattern.
Keep going
How every figure on this page is calculated
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Find what replaces your water heater
Enter the model number off your old unit and see what is on file today, with the yearly cost difference.
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Find a water heater that fits
Three questions — fuel, hot water need, install space — narrow every model on file to the ones that fit.
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What a water heater costs to run
Prices a unit's efficiency against your own utility's filed tariff for your ZIP code.
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How to size a tankless water heater by GPM
Answered from what models in this size actually file.
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Water heaters
Every model on file with the Department of Energy, by heater type.
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All gas tankless water heaters
Gas-fired instantaneous units, sized by flow rate rather than tank gallons.
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Every RELIANCE WATER HEATERS model on file
What this brand files, by heater type.
UEF 0.91 · Grade C Price it on your ZIP
The figure of 122 therms is computed by this site, not published by the registry. The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.91. This site applies it to the daily hot-water draw that the DOE test uses for the medium pattern. The draw is identical for every model in that pattern, so the figure compares units and does not predict any single home. A home that draws more or less hot water than the test's daily amount will use a different number of therms. The fuel is natural gas, and the source is DOE CCD, retrieved 2026-09-19.
Against the 80 models registered as a gas tankless unit at the medium draw pattern, the class median is 135 therms. This model sits 13 therms below that median. Its rank is 4th lowest energy use of 80, which is in the lowest quarter of its class. The figure suits a household near the medium pattern and says little about a home whose daily use differs from the test. Its maximum flow rate in gallons per minute is 3.5, a separate registry value that is not part of the energy figure. A household with a different pattern can compare other units with the selector by fuel, space and size. To find a same-class unit for this model, use the replacement search by model number.
The running cost is not stated here because it depends on your state's average residential gas price. For a household at the medium pattern, multiply 122 therms by your own rate per therm. The cost calculator does this from your ZIP. You can read how the annual cost is calculated on the methodology page. The installed price range appears in its own block with its source and date, as a modeled range and not a quote. Whether 13 therms below the class median matters in practice depends on your gas rate, and the registry does not give a rate. Measured use in your home is not available in this data.
DOE CCD · 2026-09-19