Navien NPE-240S2 vs State ATHR-180M 1 (STHR-180M 1)
The Navien NPE-240S2 is the more efficient unit: UEF 0.96 versus 0.95 — about 1% less energy for the same hot water. At national average rates that works out to about $255/year for the Navien NPE-240S2 against $258/year for the State ATHR-180M 1 (STHR-180M 1) — a $3 annual difference. The Navien NPE-240S2 sustains the higher flow (5.8 GPM vs 5.3 GPM under the DOE test).
| Navien NPE-240S2 | State ATHR-180M 1 (STHR-180M 1) | |
|---|---|---|
| Uniform Energy Factor (UEF) | 0.96 | 0.95 |
| Fuel | Natural Gas, Propane | Natural Gas, Propane |
| Max flow rate | 5.8 GPM | 5.3 GPM |
| Draw pattern | High | High |
| Annual gas use (natural gas) | 176 therms/yr | 178 therms/yr |
| Gas input rate | 199 kBTU/h | 180 kBTU/h |
| Max current draw | 5 A | 5 A |
| Vent type | Power Direct Vent | Power Vent, Power Direct Vent |
| Recovery efficiency | — | 97 % |
| Smart / connected capable | No | No |
| Minimum activation flow | 1 GPM | 1 GPM |
| Annual propane use | 192.35 gal/yr | 194.53 gal/yr |
| Vent size | 2 | 3 / 2 |
| Height | 27 in | — |
| Width | 17 in | 17 in |
| Depth | 13 in | 16 in |
| ENERGY STAR certified | Yes | Yes |
Frequently asked questions
Which costs less to run, the Navien NPE-240S2 or the State ATHR-180M 1 (STHR-180M 1)?
The Navien NPE-240S2: about $255/year versus $258/year for the State ATHR-180M 1 (STHR-180M 1) at national average rates — a $3 annual difference.
Are the Navien NPE-240S2 and State ATHR-180M 1 (STHR-180M 1) both ENERGY STAR certified?
Yes — every water heater in this database is drawn from the U.S. EPA ENERGY STAR certified water heater datasets.