RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1)

RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) is a gas tankless water heater from RELIANCE WATER HEATERS rated 5.3 GPM at a 0.95 UEF — 178 therms/yr certified use, 180k BTU/h input.

Also sold as the A. O. Smith ATHR-180M 1. This model is the same certified hardware as the A. O. Smith ATHR-180M 1, published under a different brand — full details, comparisons, and pricing live on that page. The certified figures below are identical.

Efficiency
Uniform Energy Factor (UEF) 0.95
Annual gas use (natural gas) 178 therms/yr
Recovery efficiency 97 %
Annual propane use 194.53 gal/yr
General
Fuel Natural Gas, Propane
Capacity
Max flow rate 5.3 GPM
Draw pattern High
Minimum activation flow 1 GPM
Performance
Gas input rate 180 kBTU/h
Installation
Max current draw 5 A
Vent type Power Vent, Power Direct Vent
Vent size 3 / 2
Smart features
Smart / connected capable No
Dimensions
Width 17 in
Depth 16 in
Certification
ENERGY STAR certified Yes

Real flow rate by climate

A tankless heater's usable flow depends on how far it must raise incoming water temperature. Sustained hot-water flow of the RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) at common temperature rises (a typical shower uses about 2 GPM of mixed water):

Temperature rise Climate Sustained flow Simultaneous showers
45 °F Warm climate (~75 °F groundwater) 5.3 GPM 2
55 °F Mild climate (~65 °F groundwater) 5.3 GPM 2
70 °F Cold climate (~50 °F groundwater) 4.9 GPM 2
77 °F DOE test condition 4.4 GPM 2

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Frequently asked questions

Is the RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) ENERGY STAR certified?

Yes, the RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) holds a current ENERGY STAR certification for water heating efficiency (UEF 0.95).

How much does the RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) cost to run per year?

About $258 per year at national average energy rates, based on its certified annual energy use under the DOE test draw pattern. Your rate and usage change this figure.

What venting does the RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) use?

The RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) uses Power Vent, Power Direct Vent venting with 3 / 2 in vent connections. Matching the existing vent type is usually the cheapest replacement path.

Is the RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) a smart water heater?

No, the RELIANCE WATER HEATERS ATHR-180M 1 (RTHR-180M 1) is not connected-capable — it has no app connectivity or demand-response support.

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