A. O. Smith Water Heaters
The widest retail gas range in America, and a warranty trade-off nobody points out.
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A. O. Smith makes the widest range of gas tanks on retail shelves, with the best published first-hour ratings here: 91 gallons from a 50-gallon, 50,000 BTU Signature 100. Its Voltex heat pumps top this site's efficiency table at 4.02 UEF. The catch to know: on the Signature line the longer warranty is on the smaller burner.
A. O. Smith Corporation is one of the two companies that dominate American water heating. Beyond its own badge it makes State, markets American Water Heaters, Reliance and Takagi in North America, and acquired Lochinvar in 2011 in what was then its largest acquisition.
The line-up, as it matters to a buyer
| Range | Type | What it is for |
|---|---|---|
| Signature 100 | Gas and electric tanks, retail | The mainstream replacement range, sold at Lowe's |
| Voltex AL | Heat pump | Highest published efficiency here at 4.02 UEF, 10-year anode |
| Voltex MAX | Heat pump | Highest first-hour rating here at 83 gallons, 3.84 UEF |
| ProLine XE | Heat pump | Entry into 66-gallon heat pump capacity, 3.42 UEF, 6-year anode |
Quick picks
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| # | Product | Best for | Price |
|---|---|---|---|
| 1 | A. O. Smith Signature 100, 50 gal gasThe straightforward 50-gallon gas replacement, and the reason to pay attention to the burner size: the 50,000 BTU version is rated at a 91-gallon first-hour rating against 77 gallons for the 40,000 BTU one. | Most gas tank replacements | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 2 |  A. O. Smith Voltex AL, 66 galThe efficiency leader on this page at 4.02 UEF, in the capacity that suits a five- or six-person household, with a heavy-duty anode rated to protect the tank for 10 years. | Highest published heat pump efficiency | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 3 |  A. O. Smith Voltex MAX, 66 galAn 83-gallon first-hour rating at a 3.84 UEF — the heat pump water heater for a household that runs several showers back to back and still wants the running cost of a heat pump. | Largest first-hour rating | Check price on Amazon No live price feed on this site, so we show none. #ad |
| 4 |  A. O. Smith ProLine XE, 66 galThe entry point into 66-gallon heat pump capacity: 3.42 UEF and a 79-gallon first-hour rating, with a 6-year anode instead of the Voltex line's 10. | Cheapest route into a large heat pump | Check price on Amazon No live price feed on this site, so we show none. #ad |
The picks in full
Pick 1 — Most gas tank replacements
A. O. Smith Signature 100, 50 gal gas
The straightforward 50-gallon gas replacement, and the reason to pay attention to the burner size: the 50,000 BTU version is rated at a 91-gallon first-hour rating against 77 gallons for the 40,000 BTU one.
| Capacity | 50 gallons |
|---|---|
| First-hour rating | 91 gallons (50,000 BTU model); 77 gallons (40,000 BTU model) |
| Burner | 50,000 BTU/h ultra-low NOx, or 40,000 BTU/h |
| Dimensions | 61 in H x 22 in dia (50,000 BTU); 60-3/4 in H x 22 in dia (40,000 BTU) |
| Warranty | 6-year tank and parts with 1-year labor (50,000 BTU); 9-year tank and parts with 2-year labor (40,000 BTU) |
What is good
- A 91-gallon first-hour rating from a 50-gallon tank covers back-to-back showers that empty an electric tank of the same size
- Widely stocked at Lowe's, so same-day replacement is realistic when the old one fails
- Ultra-low NOx burner meets the stricter air-district rules in California and Texas
- 22-inch diameter fits most existing alcoves without re-plumbing
What is not
- The longer 9-year warranty is on the smaller burner, so warranty and recovery pull in opposite directions
- Atmospheric venting needs a working chimney or B-vent
- Standing pilot and flue losses mean it idles energy away all day
Skip it if: Skip it if your water heater sits in a sealed closet or a space with combustion air problems. An atmospheric gas tank needs real combustion air and a real flue — the power-vent or direct-vent models exist for exactly that case.
No live price feed on this site, so we show none. #ad
Specifications above from Lowe's listing, Signature 100 50-gal 50,000 BTU; Lowe's listing, Signature 100 50-gal 40,000 BTU 9-year. We have not tested this unit ourselves.
Pick 2 — Highest published heat pump efficiency
A. O. Smith Voltex AL, 66 gal
The efficiency leader on this page at 4.02 UEF, in the capacity that suits a five- or six-person household, with a heavy-duty anode rated to protect the tank for 10 years.
| Capacity | 66 gallons |
|---|---|
| Efficiency | 4.02 UEF |
| Anode | Heavy-duty, rated to protect the tank for 10 years |
| Warranty | 10-year limited |
| Certification | ENERGY STAR certified |
What is good
- 4.02 UEF is the highest figure of any unit in this registry
- 66 gallons removes the recovery anxiety that a 50-gallon heat pump creates in a big household
- The 10-year anode is a real durability claim, not a marketing one
- ENERGY STAR certification keeps it inside most utility rebate lists
What is not
- 66 gallons is a tall, wide cabinet — measure the space before you order
- Sold mainly through wholesale, so availability is slower than big-box
- Published first-hour rating is not listed for the AL model; the Voltex MAX at the same capacity is rated at 83 gallons
Skip it if: Skip it if your install space is a closet. A 66-gallon heat pump needs air volume to work, and starving a heat pump water heater of air is how you end up running on the backup element and paying resistance rates for a premium appliance.
No live price feed on this site, so we show none. #ad
Specifications above from Auer Steel listing, A. O. Smith HPTS-66 Voltex AL; A. O. Smith Voltex AL introduction. We have not tested this unit ourselves.
Pick 3 — Largest first-hour rating
A. O. Smith Voltex MAX, 66 gal
An 83-gallon first-hour rating at a 3.84 UEF — the heat pump water heater for a household that runs several showers back to back and still wants the running cost of a heat pump.
| Capacity | 66 gallons |
|---|---|
| First-hour rating | 83 gallons |
| Efficiency | 3.84 UEF |
| Certification | ENERGY STAR certified |
What is good
- 83 gallons in the first hour beats an 80-gallon resistance tank
- 3.84 UEF is still roughly four times a resistance tank
- 66 gallons of storage plus fast recovery is the combination big households actually need
- ENERGY STAR certified for rebate eligibility
What is not
- Lower UEF than the Voltex AL at the same capacity — you are trading some efficiency for delivery
- Large footprint
- Wholesale distribution
Skip it if: Skip it if two people live in the house. You would be buying 66 gallons and an 83-gallon first-hour rating to serve a demand a 50-gallon unit covers, and paying standby losses on the difference every day for a decade.
No live price feed on this site, so we show none. #ad
Specifications above from First Supply listing, A. O. Smith HPTA-66 Voltex MAX. We have not tested this unit ourselves.
Pick 4 — Cheapest route into a large heat pump
A. O. Smith ProLine XE, 66 gal
The entry point into 66-gallon heat pump capacity: 3.42 UEF and a 79-gallon first-hour rating, with a 6-year anode instead of the Voltex line's 10.
| Capacity | 66 gallons |
|---|---|
| First-hour rating | 79 gallons |
| Efficiency | 3.42 UEF |
| Anode | Heavy-duty, rated to protect the tank for 6 years |
| Certification | ENERGY STAR certified |
What is good
- 79-gallon first-hour rating for the lowest price of the three 66-gallon units here
- 3.42 UEF is still a step change from any resistance tank
- ENERGY STAR certified
- Same large capacity as the Voltex models
What is not
- The 6-year anode rating is the clearest difference from the Voltex line, and anodes are what tanks die from
- Lowest UEF of the heat pump units listed here
- Wholesale distribution
Skip it if: Skip it if your water is hard or softened. Anode life is what decides when the tank leaks, and in aggressive water the 6-year anode rating is the figure that will come back to bite you — pay for the Voltex AL's 10-year anode instead.
No live price feed on this site, so we show none. #ad
Specifications above from First Supply listing, A. O. Smith FPTU-66 ProLine XE Voltex. We have not tested this unit ourselves.
The Signature 100 trade-off, in one table
This is the thing worth knowing before you stand in front of the shelf. Two 50-gallon Signature 100 gas models, same name, very different propositions:
| Burner | First-hour rating | Warranty | Height x diameter |
|---|---|---|---|
| 50,000 BTU ultra-low NOx | 91 gal | 6-year tank and parts, 1-year labor | 61 in x 22 in |
| 40,000 BTU | 77 gal | 9-year tank and parts, 2-year labor | 60-3/4 in x 22 in |
Fourteen gallons of first-hour delivery against three years of tank coverage. For a four-person household the 40,000 BTU unit with the 9-year warranty is arguably the better buy; for five people, take the recovery. Nobody in the aisle will tell you this, and both boxes say Signature 100.
Where A. O. Smith is strongest
- Retail gas tanks. The range is wide, availability is good, and the published first-hour ratings are the best here.
- Heat pump efficiency. The Voltex AL's 4.02 UEF is the highest figure in our registry.
- Heat pump delivery. The Voltex MAX's 83-gallon first-hour rating beats an 80-gallon resistance tank.
- Anode durability on the premium line. The Voltex AL's heavy-duty anode is rated to protect the tank for 10 years against 6 on the ProLine XE — and anode life is what decides when a tank fails.
- Ultra-low NOx availability, which matters in California and parts of Texas where it is required.
Where it is weaker
- Published data on the heat pump line is patchy. The Voltex AL's first-hour rating and ambient operating range were not on the distributor listings we could read, where Rheem publishes both prominently. For a cold-space install that is a real gap.
- The warranty-versus-burner trade on the Signature line is poorly signposted at point of sale.
- No tankless of its own in the sense that matters here — it markets Takagi rather than engineering a competing line under its own badge.
- Brand proliferation means a Signature, a State and an American unit can be hard to tell apart on substance.
The sibling brands
A. O. Smith's portfolio means several badges share a parent. State is its own brand under the same corporate roof; American Water Heaters and Reliance are marketed by it in North America; Takagi tankless units are distributed by it; and Lochinvar, acquired in 2011, is primarily a boiler brand where roughly 45% of branded sales are water heaters.
For a buyer that means comparing A. O. Smith against State is not the independent comparison it appears to be. State water heaters.
What goes in with it
A water heater is a system, not a box. These are the parts that go in with it, and the ones people discover they need halfway through the job.
- Expansion tank
Required by code on a closed system, which is most homes with a pressure-reducing valve.
- Drain pan
Cheap insurance anywhere the tank sits above something you care about.
- Anode rod
The part that decides when the tank leaks. Replacing it is the highest-value hour of maintenance there is.
Our verdict
Buy A. O. Smith for a retail gas tank replacement, where the Signature 100 50-gallon at 50,000 BTU and its 91-gallon first-hour rating is hard to beat. Buy the Voltex AL if maximum heat pump efficiency and a 10-year anode are the priority and the install space is warm. For a cold garage, we would take the Rheem ProTerra instead, purely because its ambient operating range is published.