A. O. Smith HPACO-45 1**+AXST-50S 1**
A. O. Smith HPACO-45 1**+AXST-50S 1** is in the DOE listing as of Oct 26, 2026 and is in the ENERGY STAR list as of Oct 26, 2026.
It has a labeled size of 45 gallons, a certified storage volume of 46 gallons, a certified UEF of 3.52, and a certified first-hour rating of 70 gallons of hot water.
- Heat pump water heater
- 4 listed models
Certified figures
- Storage volume
- 46gallons
- UEF
- 3.52Uniform energy factor
- First-hour rating
- 70gallonsHot water in the first hour
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Change your hourProduct history
A. O. Smith HPACO-45 1**+AXST-50S 1** was in the DOE listing by Oct 1, 2026.
A. O. Smith HPACO-45 1**+AXST-50S 1** has a recorded ENERGY STAR market-availability date of Feb 13, 2026. It first appeared in the ENERGY STAR list between February 2026 and August 2026.
Certified figures by listed model
| Model number | Storage volume (gal) | UEF | First-hour rating (gal) | Recovery efficiency | Draw pattern |
|---|---|---|---|---|---|
| HPACO-45 1**+AXST-50S 1** | 46 | 3.52 | 70 | 429% | Medium |
| HPACO-45 1**+AXST-50STTP 1** | 46 | 3.52 | 70 | 429% | Medium |
| HPACO-45C 1**+AXST-50SC 1** | 46 | 3.52 | 70 | 429% | Medium |
| HPACO-45C 1**+AXST-50SCTTP 1** | 46 | 3.52 | 70 | 429% | Medium |
UEF is the uniform energy factor. A dash means the model has no such figure.
ENERGY STAR certified models
| Model number | Storage volume (gal) | UEF | First-hour rating (gal) | Recovery efficiency |
|---|---|---|---|---|
| HPACO-45 1**+AXST-50S 1** | 46 | 3.52 | 70 | 429% |
| HPACO-45 1**+AXST-50STTP 1** | 46 | 3.52 | 70 | 429% |
| HPACO-45C 1**+AXST-50SC 1** | 46 | 3.52 | 70 | 429% |
| HPACO-45C 1**+AXST-50SCTTP 1** | 46 | 3.52 | 70 | 429% |
It holds 46 gallons in the test, 1 gallon more than its 45-gallon sold size. Starting full, it gives 70 gallons of hot water in its first hour of use. Its tank holds 46 gallons, so reheating adds 24 gallons during the first hour. Of 481 heat pump models, 251 give more hot water in the first hour. Among heat pump models, the median first-hour rating is 72 gallons.
Under this basic model, 4 model numbers are ENERGY STAR certified. In the test, it gives 3.52 units of hot water energy per unit it uses (its UEF). A UEF above 1 is possible because it moves heat from the air into the water. In the test, daily hot water use was set to medium (its draw pattern). Its UEF is lower than that of 143 of the 226 heat pump models with its draw pattern. A UEF of 3.68 is the median for its type and draw pattern. When it reheats water in the test, the water gains 429% of the energy it uses.
A tag or quote may show any of its 4 model numbers. Its test figures match those of 8 other basic models. In all, 7 other brands list one or more of them.
It may qualify for 17 rebate programs. It may qualify for 5 more if it meets terms its figures do not show.
Also listed as
They carry every figure in the table above.
- American HPACO-45 1**+AXST-50S 1**
- Giant HPACO-45 1**+AXST-50S 1**
- GSW WATER HEATERS HPACO-45 1**+AXST-50S 1**
- John Wood HPACO-45 1**+AXST-50S 1**
- John Wood JWHPCO-45 1**+JWXST-50S 1**
- Lochinvar HPACO-45 1**+AXST-50S 1**
- RELIANCE WATER HEATERS HPACO-45 1**+AXST-50S 1**
- State HPACO-45 1**+AXST-50S 1**
Rebates
Programs change their terms. Check the program's own page before you buy.
- Every A. O. Smith basic model
- Every 40-gallon heat pump water heater
- Every heat pump water heater
- The most-searched heat pump models side by side
Not covered
- Advertised figures. We have none on file for this model.