A. O. SMITH HPACO-45 1**+AXST-50T 1**
3.52 UEF DOE CCD · 2026-09-19Grade B: where this UEF sits among the 426 models in its class, lowest (G) to highest (A). A position, not an official label. How the grade is set
An electric tank, medium draw pattern (a typical three- or four-person household, about 55 gallons on a busy morning).
For a check on this model: A. O. SMITH HPACO-45 1**+AXST-50T 1** uses 923 kWh a year at the medium draw pattern, the standard daily hot-water usage DOE tests against. That is 2,608 kWh below the class median of 3,531 kWh across 426 electric tank models.
Energy use per year
923 kWh a year
Computed by this site from the registry's UEF and the federal test's daily hot-water draw for this draw pattern. What it costs depends on the electricity rate where you live.
That is below the median of 3,531 kWh for the 426 models registered in the same heater type and draw pattern; it ranks 70 of 426, lowest energy first.
Solid line: this model (923 kWh). Dashed line: the class median.
Min 773 kWh Median 3,531 kWh Max 3,569 kWh
What it costs to run where you live
What the registry files
- UEF (Uniform Energy Factor) how much hot water you get for each unit of energy the heater uses
- 3.52 DOE CCD · 2026-09-19 Compared only with other models registered as an electric tank at the medium draw pattern.
- Draw Pattern the standard daily usage profile DOE tests the unit against
- Medium DOE CCD · 2026-09-19
- First Hour Rating how many gallons of hot water the unit can deliver in one hour, starting from a full tank
- 67 gal DOE CCD · 2026-09-19
- Rated Storage Volume the tank size in gallons
- 45 gal DOE CCD · 2026-09-19
- On the market since (ENERGY STAR) the date the manufacturer told ENERGY STAR the model went on sale
- 2026-02-13 ENERGY STAR · 2026-09-19
- Connected / demand response (ENERGY STAR) whether the unit can take signals from your utility to shift when it heats, and by which standard (such as CTA-2045)
- Yes (CTA-2045-A,CTA-2045-B) ENERGY STAR · 2026-09-19
- Refrigerant and GWP (ENERGY STAR) the refrigerant a heat pump unit uses and its global warming potential, a leak's climate effect relative to carbon dioxide (CO2 = 1)
- R-744 (CO2), GWP 1 ENERGY STAR · 2026-09-19
What it costs to install
$2,998–$4,170 installed
Not a quote — a modeled range of what installers have charged for this class of unit; your price will vary with labor rates, access, and local code requirements.
Escalation indexes: equipment (BLS PPI) latest available: August 2026; labor (BLS ECI) latest available: April 2026 to June 2026.
NLR REMDB (BLS PPI/ECI escalated) · 2026-04-01Safety record
No CPSC recall names this model.
Checked against the CPSC recall database. CPSC does not publish a model-level match for this product category, so this list is curated by hand from the manufacturer's recall filings.
CPSC · 2026-09-24Does it fit your space?
Enter your own numbers below — this compares them to what ENERGY STAR publishes for this model, it does not tell you what to buy.
- Compressor operating range (ENERGY STAR)
- the air temperatures around the unit in which its heat pump runs; outside this range the heat pump stops
- Dimensions (ENERGY STAR)
- the unit's filed height, width, depth or tank diameter, in inches
- Input voltage and maximum current (ENERGY STAR)
- the circuit voltage the unit is certified on and the most current it draws
What these figures mean
How this compares
The closest models in the same class — same fuel, type and draw pattern.
Keep going
How every figure on this page is calculated
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Find what replaces your water heater
Enter the model number off your old unit and see what is on file today, with the yearly cost difference.
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Find a water heater that fits
Three questions — fuel, hot water need, install space — narrow every model on file to the ones that fit.
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What a water heater costs to run
Prices a unit's efficiency against your own utility's filed tariff for your ZIP code.
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What size heat pump water heater do I need?
Answered from what models in this size actually file.
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Water heaters
Every model on file with the Department of Energy, by heater type.
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All heat pump water heaters
Electric tanks that file a UEF of 2.0 or more — the registry has no separate heat pump type, so this site draws the line there.
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All CO₂ (R-744) heat pump water heaters
Heat pump models whose ENERGY STAR filing names R-744 (carbon dioxide) as the refrigerant, a global warming potential of 1.
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Every A. O. SMITH model on file
What this brand files, by heater type.
UEF 3.52 · Grade B Price it on your ZIP
The registry lists a UEF, the ratio of hot water delivered to energy used, of 3.52 for this model. This site combines that value with the DOE test's daily hot-water draw for the medium pattern. The result is 923 kWh of electricity a year, computed by this site and not published by the registry. The class median is 3,531 kWh, so this model sits 2,608 kWh below it. Its rank is 70th lowest energy use of 426 models, in the lowest quarter of its class. The comparison covers only models registered as an electric tank at the medium draw pattern. The source is DOE CCD, retrieved 2026-09-19.
The figure of 923 kWh applies to the medium draw pattern only. A household that uses more hot water than that pattern would use more energy than the figure shows. A household that uses less would use less. The registry lists a first hour rating, the gallons of hot water available in the first hour from a full tank. It is 67 gallons for this model, and the rated volume is 45 gallons. This data does not show a household's peak demand, so it cannot say whether that rating is enough. To compare options, use the water heater selector by fuel, space and size. To find a same-class replacement, use the lookup by model number.
The running cost is not stated here. It depends on your own utility electricity tariff. Multiply 923 kWh by your rate per kilowatt-hour to get a yearly cost at the medium draw pattern. The cost calculator on your own ZIP does this for you. At the same rate, a model at the class median of 3,531 kWh would cost more in proportion to the extra 2,608 kWh. The steps are described under how the annual cost is calculated. The modeled installed-cost range appears in its own block with its source and date. It is a modeled range, not a quote, and this text does not restate it.
DOE CCD · 2026-09-19