RELIANCE WATER HEATERS TK-310U-I 2**
0.81 UEF DOE CCD · 2026-09-19Grade G: where this UEF sits among the 397 models in its class, lowest (G) to highest (A). A position, not an official label. How the grade is set
A gas tankless unit, high draw pattern (a larger household, or one where showers and laundry overlap).
If you are checking this unit's figures, the RELIANCE WATER HEATERS TK-310U-I 2**, a gas tankless unit, uses 209 therms of natural gas a year. That figure applies at the high draw pattern, the standard daily hot-water usage DOE tests against. It sits 27 therms above its class median of 182 therms, ranking 323rd lowest energy use of 397.
Energy use per year
209 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 above the median of 182 therms for the 397 models registered in the same heater type and draw pattern; it ranks 323 of 397, lowest energy first.
Solid line: this model (209 therms). Dashed line: the class median.
Min 173 therms Median 182 therms Max 209 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
- 0.81 DOE CCD · 2026-09-19 Compared only with other models registered as a gas tankless unit at the high draw pattern.
- Draw Pattern the standard daily usage profile DOE tests the unit against
- High DOE CCD · 2026-09-19
- Maximum Gallons Per Minute how many gallons a minute it can heat while running continuously
- 4.7 gal/min DOE CCD · 2026-09-19
What it costs to install
$1,698–$2,632 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 0.81 · Grade G Price it on your ZIP
The 209 therms figure is computed by this site, not published by the registry. It combines the registry's UEF, the ratio of hot water delivered to energy used, with the DOE test's daily hot-water draw for the high draw pattern. For this model the UEF is 0.81, from the DOE CCD, retrieved 2026-09-19. The figure holds only at the federal test's daily draw. A household that draws more or less hot water will use a different amount of gas, and that amount is not available here. The comparison class is the 397 models registered as a gas tankless unit at the high draw pattern. Within that class, this model is in the highest quarter for energy use. The page on how the annual cost is calculated explains the method behind these figures.
The high draw pattern describes a larger household, or one where showers and laundry overlap. The 209 therms figure is most relevant to a home that matches that description, because that is the usage the test assumes. The TK-310U-I 2** has a maximum flow rate in gallons per minute of 4.7, as listed in the registry. Whether 4.7 covers a given home's overlapping showers and appliances depends on the fixtures in use. This page does not have that information, so it cannot confirm the fit for a specific house. A reader who wants to compare other units by fuel, space and size can use the selector by fuel, space and size. That tool lists models beyond this gas tankless class.
For a reader whose priority is lower gas use, the 323rd position out of 397 matters. Models ranked below it in the same class use less gas at the high draw pattern. This page does not state the running cost, because it depends on the reader's state average residential gas price. The page computes it from the reader's ZIP instead. The cost calculator on your own ZIP applies that rate to the 209 therms figure. The installed price range appears in its own block, with its source and date. It is a modeled installed-cost range, not a quote. To check which other models share this class, use find a same-class replacement by model number with TK-310U-I 2**.
DOE CCD · 2026-09-19