A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1)
A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) is a heat pump (hybrid electric) water heater from A. O. Smith with a 48 gallon rated tank and a 72 gallon first-hour rating at a 3.55 UEF — 915 kWh/yr certified use, 33 in tall.
Our take
A true lowboy: the indoor tank of this CO₂ split system stands 33 inches — the shortest heat-pump water heater in this database, half the height of some classmates — because the compressor lives outdoors. That outdoor unit runs to 1 °F before any cutoff, and the R-744 refrigerant has a GWP of 1. Certified performance is solid mid-class: 3.55 UEF (the median exactly), about $156 a year, a 72-gallon first-hour rating well above the median. Eight brand names certify it. Crawl spaces and under-stair closets are suddenly candidates.
Best for: Installs under 3 feet of clearance no integrated unit can touch.
Trade-off: Split-system plumbing and an outdoor unit raise install scope and cost.
Efficiency
Uniform Energy Factor (UEF)
3.55
Annual electricity use
915 kWh/yr
Recovery efficiency
428 %
General
Fuel
Electric
Capacity
First-hour rating
72 gal
Rated storage volume
48 gal
Draw pattern
Medium
Heat pump
Heat pump type
Split System HPWH
Refrigerant (GWP)
R-744 (CO₂) (GWP:1 | Lower GWP)
Compressor low-temp cutoff
1 °F
Installation
Input voltage
240
Max current draw
20.2 A
Smart features
Smart / connected capable
Yes
Dimensions
Height
33 in
Diameter
22.5 in
Certification
ENERGY STAR certified
Yes
Who is the A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) for?
Its 72 gallon first-hour rating suits a
household of 3–4 people under DOE sizing guidance.
Estimated running cost: about $156/year at the national
average electricity rate (915 kWh/yr certified use).
Needs a 240 V circuit; at 20.2 A max draw plan for a 30 A breaker (NEC 125% continuous-load rule).
The heat pump compressor operates down to 1 °F ambient — below that, backup
elements take over.
Also sold as
The A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) is certified hardware that A. O. Smith and its partner brands
publish under 9 names. The same specifications apply to every
variant:
Is the A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) ENERGY STAR certified?
Yes, the A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) holds a current ENERGY STAR certification for water heating efficiency (UEF 3.55).
How much does the A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) cost to run per year?
About $156 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 electrical circuit does the A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) need?
The A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) runs on a 240 V circuit drawing up to 20.2 A; per the NEC 125% continuous-load rule plan for at least a 30 A breaker (check the installation manual for the required circuit).
Is the A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) a smart water heater?
Yes, the A. O. Smith Split System Heat Pump 50-Gallon (HPACO-45 1-+AXST-50LBTTP 1) is connected-capable, with app control and eligibility for most utility demand-response programs.
