DoesTheMath

A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1**

3.55 UEF DOE CCD · 2026-09-19
B

Grade 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 anyone verifying this listing, the A. O. SMITH HPACO-45 1**+AXST-50LBTTP 1** uses 915 kWh of electricity a year. That figure is for the medium draw pattern, the standard daily hot-water usage DOE tests against. It is 2,616 kWh below the class median of 3,531 kWh.

Energy use per year

915 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 60 of 426, lowest energy first.

This model: 915 kWh

Solid line: this model (915 kWh). Dashed line: the class median.

Min 773 kWh Median 3,531 kWh Max 3,569 kWh

DOE CCD · 2026-09-19

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What it costs to run where you live

Enter your ZIP to see what this unit costs to run a year on your own utility’s electricity rate.

What the registry files

UEF (Uniform Energy Factor) how much hot water you get for each unit of energy the heater uses
3.55 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
72 gal DOE CCD · 2026-09-19
Rated Storage Volume the tank size in gallons
48 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

$3,099–$4,228 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) · 2026-04-01

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Safety 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 · 2026-09-24

Every water heater recall on file since 2015

Does 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
  • Ambient temperatureEnter your numbers1°F min
  • Physical footprintEnter your numbers22.5" ⌀
  • Electrical supplyEnter your numbers240V, 20.2A max
 ENERGY STAR · 2026-09-19

What these figures mean

This site computes the annual figure; the registry does not list it. The calculation starts from the registry's UEF, the ratio of hot water delivered to energy used. It then applies the daily hot-water draw that the DOE test uses for the medium draw pattern. The registry lists a UEF of 3.55 for this model. The result is 915 kWh of electricity a year, retrieved from DOE CCD on 2026-09-19. The medium draw pattern represents a typical three- or four-person household. The methodology page sets out how the annual cost is calculated.

Among the 426 models registered as an electric tank at the medium draw pattern, this one ranks 60th lowest for energy use. That places it in the lowest quarter of its class. The gap to the class median is 2,616 kWh a year under the same test conditions. Its first hour rating, the gallons of hot water available in the first hour from a full tank, is 72 gallons. The rated volume is 48 gallons. The energy figure suits a household that matches the medium draw pattern. It says less about households with much heavier or lighter use, because the test draw is fixed. The water heater selector filters models by fuel, space and size.

The running cost is not stated here because it depends on your own utility electricity tariff. Multiply 915 kWh by your rate per kilowatt-hour for a yearly figure at the test draw. The cost calculator does this from your ZIP. Your actual use will differ from 915 kWh if your hot-water use differs from the medium draw pattern. The installed price range appears in its own block with its source and date. It is a modeled range, not a quote, and this page does not restate it. For a same-class replacement, try the replacement lookup by model number.

DOE CCD · 2026-09-19

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

UEF 3.55 · Grade B Price it on your ZIP

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