GSW WATER HEATERS ATHR-199M 1**
0.95 UEF DOE CCD · 2026-09-19Grade B: 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).
Checking this unit's energy use: the GSW WATER HEATERS ATHR-199M 1**, a gas tankless unit, uses 178 therms of natural gas a year at the high draw pattern, the standard daily hot-water usage DOE tests against. That is 4 therms below the class median of 182 therms, among 397 registered models.
Energy use per year
178 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 45 of 397, lowest energy first.
Solid line: this model (178 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
- 0.95 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
- 5.9 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
- 2024-02-01 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
$2,358–$3,405 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 GSW WATER HEATERS model on file
What this brand files, by heater type.
UEF 0.95 · Grade B Price it on your ZIP
The GSW WATER HEATERS ATHR-199M 1** has a UEF, the ratio of hot water delivered to energy used, of 0.95. This site combines that registry value with the DOE test's daily hot-water draw for the high draw pattern to reach 178 therms of natural gas a year. The registry does not state the annual figure; this site computes it, and how the annual figure is calculated is described separately. The source is DOE CCD, retrieved 2026-09-19. The class is the 397 models registered as a gas tankless unit at the high draw pattern, and its median is 182 therms. This model sits 4 therms below that median. It ranks 45th lowest in energy use of 397, which places it in the lowest quarter of its class for energy use.
The high draw pattern describes a larger household, or one where showers and laundry overlap. The energy figure applies to that pattern only. A household with a different daily hot-water use will use a different amount of gas, and this page has no figure for other draw patterns. The unit's maximum flow rate in gallons per minute is 5.9. This page does not show the flow available at a given temperature rise, so that value is not available here. The difference from the class median is 4 therms on a median of 182 therms, so this figure shows that difference and nothing about performance at other draw patterns. To narrow models by fuel, space and size, use the water heater selector.
The running cost is not stated in the text because it depends on your state's average residential gas price. Multiply 178 therms by that price per therm to get the yearly gas cost of the ATHR-199M 1** at the high draw pattern. The cost calculator does this from your ZIP code. The modeled installed-cost range appears in its own block on this page, with its source and date, as a range and not a quote, so it is not restated here. If you need a model in the same class to compare against ATHR-199M 1**, you can find a same-class replacement by model number. Any cost derived from the energy figure follows the DOE test's daily draw and is not a measurement of your own home's use.
DOE CCD · 2026-09-19