A. O. Smith ACTH-199M-(N,P) 1 is a gas tankless water heater from A. O. Smith rated 5.8 GPM at a 0.95 UEF — 178 therms/yr certified use, 199k BTU/h input.
Our take
A full-size 199 kBTU condensing unit whose calling card is installation flexibility: certified for both power-vent and power-direct-vent configurations over 2- or 3-inch pipe, and for both natural gas and propane. Output sits on the class medians — 5.8 GPM rated, about 5.4 GPM sustained at a cold-climate 70 °F rise, enough for two showers and a sink — with 97% recovery efficiency. The 0.95 UEF trails the 0.96 cohort median slightly, at roughly $258 a year on natural gas. Four brand names certify this identical hardware. Activation requires 1 GPM.
Best for: Whole-house retrofits that must adapt to the existing vent layout.
Trade-off: A point of UEF and $3 a year behind the class median.
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
5.8 GPM
Draw pattern
High
Minimum activation flow
1 GPM
Performance
Gas input rate
199 kBTU/h
Installation
Max current draw
5 A
Vent type
Power Direct Vent, Power 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 A. O. Smith ACTH-199M-(N,P) 1 at common temperature
rises (a typical shower uses about 2 GPM of mixed water):
The A. O. Smith ACTH-199M-(N,P) 1 is certified hardware that A. O. Smith and its partner brands
publish under 4 names. The same specifications apply to every
variant:
Is the A. O. Smith ACTH-199M-(N,P) 1 ENERGY STAR certified?
Yes, the A. O. Smith ACTH-199M-(N,P) 1 holds a current ENERGY STAR certification for water heating efficiency (UEF 0.95).
How much does the A. O. Smith ACTH-199M-(N,P) 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 A. O. Smith ACTH-199M-(N,P) 1 use?
The A. O. Smith ACTH-199M-(N,P) 1 uses Power Direct Vent, Power Vent venting with 3 / 2 in vent connections. Matching the existing vent type is usually the cheapest replacement path.
Is the A. O. Smith ACTH-199M-(N,P) 1 a smart water heater?
No, the A. O. Smith ACTH-199M-(N,P) 1 is not connected-capable — it has no app connectivity or demand-response support.
