MIZUDO HS180A0W-NG 180,000 BTU Natural Gas Outdoor Tankless Water Heat

What it delivers

The MIZUDO HS180A0W-NG 180,000 BTU Natural Gas Outdoor Tankless Water Heater is an outdoor gas tankless with a 180,000 BTU/h burner and a stated maximum flow of 8.1 GPM.

Worked out from its input, it delivers roughly 6.2 GPM when the water only has to rise 45°F, and 4.0 GPM at a 70°F winter rise: 3 showers at 2 GPM in summer, 1 shower at 2 GPM in winter. Size it to your fixtures and climate.

Gas load at full fire: about 174 cubic feet of natural gas an hour. An older half-inch line that already feeds a furnace often can't spare that, so have a gas fitter check the pipe size and run.

Outdoor units vent straight out of the cabinet, which saves the vent run and the wall penetration; plan for freeze protection and a pipe cover where winters bite.

Other listed details: connections: 3/4" npt; material: 8.1 GPM, 180,000 BTU, Outdoor; model: HS180A0W-NG; warranty: 2-year full machine warranty, 5-year heat exchanger warranty.

The listing gives dimensions of 17.1 in (W) x 26.2 in (H).

Warranty, per the listing: 2-year full machine warranty, 5-year heat exchanger warranty.

Right unit for this house?

Install it when

One shower at a time in cold climates
Replacing a gas tank heater

Look at another unit when

More than 1 winter shower at once
Homes without a gas line

Strengths and trade-offs

Strengths

180,000 BTU/h input
Up to 8.1 GPM
No vent pipe

Trade-offs

Gas pipe sizing to confirm
Needs freeze protection outdoors
Scale builds up without flushing

Install limits

Figures are the maker's or seller's own. Flow at a rise is our estimate from the input; gas, venting and electrical work needs a licensed professional.

Rated performance

Every figure below comes from the source shown in brackets. Where the maker doesn't state something, we say so instead of estimating.

Model number	HS180A0W-NG	Retailer
Dimensions (seller)	17.1"W x 26.2"H	Retailer
Voltage	120 V	Retailer
Max flow (maker)	8.1 GPM	Retailer
Input (maker)	180,000 btu_per_hour_per_foot_per_fahrenheit	Retailer
Material	8.1 GPM, 180,000 BTU, Outdoor	Retailer
Warranty	2-year full machine warranty, 5-year heat exchanger warranty	Retailer
Fuel	Natural Gas	Retailer
Connections	3/4" npt	Retailer

Rival units at this flow

Eccotemp 7GB-NG Natural Gas Outdoor Tankless Water Heater180,000 BTU/h, up to 7.0 GPM.

Westinghouse HS180A0G-LP 180,000 BTU Propane Outdoor Tankless Water Heater180,000 BTU/h, up to 8.1 GPM.

Westinghouse HS180A0G-NG 180,000 BTU Outdoor Tankless Water Heater180,000 BTU/h, up to 8.1 GPM.

More gas tankless water heaters rated for similar demand

Full gas tankless water heaters spec grid · Every MIZUDO unit in the catalog

Final verdict

A sensible outdoor gas tankless for one shower at a time in cold climates.

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Questions buyers ask

Is the MIZUDO HS180A0W-NG 180,000 BTU Natural Gas Outdoor Tankless Water Heater big enough for two showers?

From its 180,000 BTU/h input we estimate about 6.2 GPM at a 45°F rise and 4.0 GPM at a 70°F rise, so 3 two-GPM showers with mild inlet water and 1 in a cold winter. The maker's flow chart for this model is the final word.

What size gas line does the MIZUDO HS180A0W-NG 180,000 BTU Natural Gas Outdoor Tankless Water Heater need?

At full fire it uses about 174 cubic feet of natural gas an hour. The pipe size depends on the length of the run and every other gas appliance on it; the maker's manual and a licensed gas fitter decide it.