Rheem RTGH-S10I
0.96 UEF DOE CCD · 2026-09-19Grade A: 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 the Rheem RTGH-S10I, this site calculates its annual energy use at 176 therms of natural gas. That figure applies to the high draw pattern, the standard daily hot-water usage DOE tests against. It sits 6 therms below the 182 therms median of the 397 gas tankless models registered at that pattern.
Energy use per year
176 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 182 therms for the 397 models registered in the same heater type and draw pattern; it ranks 12 of 397, lowest energy first.
Solid line: this model (176 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
- 0.96 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
- 5.2 gal/min DOE CCD · 2026-09-19
- On the market since (ENERGY STAR) the date the manufacturer told ENERGY STAR the model went on sale
- 2022-08-01 ENERGY STAR · 2026-09-19
- Connected / demand response (ENERGY STAR) whether the unit can take signals from your utility to shift when it heats, and by which standard (such as CTA-2045)
- No ENERGY STAR · 2026-09-19
What it costs to install
$2,405–$3,460 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 · 2026-09-24Does it fit your space?
Enter your own numbers below — this compares them to what ENERGY STAR publishes for this model, it does not tell you what to buy.
- Dimensions (ENERGY STAR)
- the unit's filed height, width, depth or tank diameter, in inches
- Input voltage and maximum current (ENERGY STAR)
- the circuit voltage the unit is certified on and the most current it draws
- Vent type and size (ENERGY STAR)
- how a gas unit is vented, the vent's diameter and the height of its vent connector
What 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 Rheem model on file
What this brand files, by heater type.
UEF 0.96 · Grade A Price it on your ZIP
The registry does not print the 176 therms figure. This site computed it from the model's UEF, the ratio of hot water delivered to energy used, which is listed at 0.96. The calculation combines that UEF with the daily hot-water draw that the DOE test sets for the high draw pattern. The UEF comes from the DOE CCD, retrieved 2026-09-19. This model ranks 12th lowest in energy use among the 397 gas tankless units at the high draw pattern. That rank places it in the lowest quarter of its class. The page on how the annual cost is calculated explains the full method.
The 176 therms figure applies to a household that matches the high draw pattern. That means a larger household, or one where showers and laundry overlap. The registry also lists this unit's maximum flow rate in gallons per minute at 5.2. A home that uses much less or much more hot water each day than the test assumes will not use this exact amount. This data does not include an energy figure for this model at any other draw pattern. For a home with a different pattern or fuel, use the selector by fuel, space and size. A plumber replacing this unit can find a same-class replacement by model number.
The running cost is not stated here because it depends on the reader's state average residential gas price. Instead, the page computes it from your ZIP, using the 176 therms figure at the high draw pattern. The 6 therms gap to the class median is a difference in gas use per year at that pattern, not a difference in cost. What that gap is worth changes with each state's gas price. The installed-cost range on this page is also a modeled range, not a quote. To see the running cost at your own rate, open the cost calculator for your own ZIP.
DOE CCD · 2026-09-19