Navien NPE-180S2 High Efficiency Condensing Tankless Water Heater

The Navien NPE-180S2 is a condensing tankless water heater from Navien's NPE-2 series. Same cabinet and the same pair of stainless steel heat exchangers as the NPE-180A2, without the internal pump — which is why it carries the higher efficiency rating of the two.

Rated input is 10,000 - 150,000 BTU/h on natural gas or propane — the unit is certified for both. It modulates from 150,000 BTU/h all the way down to 10,000, so it is not running at full fire to fill a sink.

How much hot water you actually get

Navien rates every tankless unit by temperature rise, because the colder the incoming water, the less of it one burner can heat. Here is what the NPE-180S2 delivers:

Temperature rise

Flow rate

Typical use

35°F

8.4 GPM

Warm-climate groundwater, or a preheated feed

45°F

6.5 GPM

The usual design point across most of the U.S.

67°F

4.3 GPM

Northern winter, incoming water near 40°F

Sized against a 2.5 GPM showerhead, the 67°F column is worth roughly one shower on the coldest day of the year, and more than that the rest of the year. Size to the 67°F row if your winter groundwater runs cold.

Minimum activation flow is 0.5 GPM, so it fires for a hand wash, not just a full shower.

Installing it

Cabinet: 17.3" W x 27.4" H x 13.2" D

Weight: 68 lbs

Water connections: 3/4" NPT cold in, 3/4" NPT hot out

Gas connection: 3/4" NPT

Water pressure range: 15-150 PSI