A. O. Smith ACTH-199M-(N,P) 1 vs Navien NPE-180S2
The Navien NPE-180S2 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-180S2 against $258/year for the A. O. Smith ACTH-199M-(N,P) 1 — a $3 annual difference. The A. O. Smith ACTH-199M-(N,P) 1 sustains the higher flow (5.8 GPM vs 4.4 GPM under the DOE test).
| A. O. Smith ACTH-199M-(N,P) 1 | Navien NPE-180S2 | |
|---|---|---|
| Uniform Energy Factor (UEF) | 0.95 | 0.96 |
| Fuel | Natural Gas, Propane | Natural Gas, Propane |
| Max flow rate | 5.8 GPM | 4.4 GPM |
| Draw pattern | High | High |
| Annual gas use (natural gas) | 178 therms/yr | 176 therms/yr |
| Gas input rate | 199 kBTU/h | 150 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 | 194.53 gal/yr | 192.35 gal/yr |
| Vent size | 3 / 2 | 2 |
| Height | — | 27 in |
| Width | 17 in | 17 in |
| Depth | 16 in | 13 in |
| ENERGY STAR certified | Yes | Yes |
Frequently asked questions
Which costs less to run, the A. O. Smith ACTH-199M-(N,P) 1 or the Navien NPE-180S2?
The Navien NPE-180S2: about $255/year versus $258/year for the A. O. Smith ACTH-199M-(N,P) 1 at national average rates — a $3 annual difference.
Are the A. O. Smith ACTH-199M-(N,P) 1 and Navien NPE-180S2 both ENERGY STAR certified?
Yes — every water heater in this database is drawn from the U.S. EPA ENERGY STAR certified water heater datasets.