A.O. Smith vs Rheem Water Heaters: Which Should You Buy

A.O. Smith and Rheem both build tank, tankless and heat pump water heaters, and both sell through other brand names you would not connect to them. Pick on what your house needs — fuel, venting, capacity — and on who stocks parts near you. If those tie, buy whichever one your local supply house actually services.

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People usually ask this question standing next to a tank that has already failed, with a decision to make that afternoon. It helps to know up front that this is not a contest between two very different products. It is a contest between two large manufacturers who compete directly, model for model, in the same categories, and who both sell under names you would not connect to them.

What Is A.O. Smith?

A. O. Smith is a water heating and water treatment manufacturer. Its own consumer site, hotwater.com, publishes a residential range covering gas tank, gas tankless, electric tank, electric tankless, hybrid electric heat pump, split system heat pump, combi boiler and solar water heater tanks, plus pressure tanks, pump storage tanks and expansion tanks.

The same site carries DOE regulation guidance, a water heater cross reference and a sizing selector — the kind of documentation that earns its keep when you are matching a replacement to a flue and a gas line you are not changing.

What Is Rheem?

Rheem Manufacturing Company builds water heating alongside heating and cooling. Its published residential water heating range covers tank water heaters, indirect tanks, tankless, heat pump water heaters (including the ProTerra line), point-of-use water heaters, boilers and combi boilers, pool and spa heating, and solar. Rheem’s corporate office is listed as 1100 Abernathy Road, Suite 1700, Atlanta, GA 30328, per the footer on its own brand sites. For a Georgia homeowner that is a piece of trivia, not a reason to buy.

A.O. Smith vs Rheem: Does the Brand on the Tank Decide Anything?

Less than the box suggests. Both companies sell into the same categories, to the same code requirements, at overlapping tiers. On real jobs the difference that shows up is not the badge. It is whether the specific model fits the space, the venting and the gas line you already have, and whether the parts counter you can drive to has the gas valve and the thermopile on the shelf. Decide the category first — tank versus tankless, then gas versus electric — then the model, then the badge.

The Other Names These Two Companies Sell Under

This is the part most buyers do not know, and it is why cross-shopping badges can mislead you. A. O. Smith’s own brands page lists American Water Heaters, State Water Heaters, Reliance Water Heaters, Lochinvar and Takagi among its brands. On the Rheem side, both Ruud and Richmond carry Rheem Manufacturing Company’s copyright and corporate address in their own site footers, and Richmond’s product registration page describes what you are registering as your Rheem heating, cooling and water heating equipment.

Read September 2026; brand line-ups do change. The practical upshot: a shelf that looks like five independent choices is often two companies.

Tank Water Heaters

For a straight tank swap the decision order is capacity, fuel, venting type, then physical fit. Both manufacturers publish those figures per model, and you should read them rather than the tier names, because tier names get rebranded and the flue collar does not.

On the gas side, the A.O. Smith GPVX-50L ProMax SL power vent gas water heater is a typical power-vent 50-gallon; on the electric side the Rheem PROE50 50-gallon professional electric water heater is the equivalent.

Two things kill more tanks than any brand difference: no thermal expansion tank on a closed system, and an anode rod nobody ever looked at. Our picks and the parts that actually matter sit on the best water heaters page.

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Tankless Water Heaters

Both sell condensing and non-condensing gas tankless units. This is where sizing mistakes hurt most, because a unit that is undersized for your winter groundwater temperature and your simultaneous-fixture load will disappoint in January no matter whose name is on the cover. Size on flow rate and temperature rise before you compare brands.

A. O. Smith’s indoor natural-gas entry is the A.O. Smith ATI-310CX3 indoor natural gas tankless water heater; the direct Rheem counterpart is the Rheem RTGH Series indoor natural gas condensing tankless water heater. See the tankless picks, and read what descaling involves before you commit — the maintenance is real on both brands.

Heat Pump Water Heaters

Both companies sell hybrid electric heat pump models: A. O. Smith lists hybrid electric heat pump and split system heat pump units, and Rheem lists heat pump water heaters including its ProTerra line. These need air volume around them, a condensate path and clearance, and they recover more slowly than gas. If you are weighing one, read heat pump versus tankless first. Choosing the wrong category costs far more than choosing the wrong brand.

Parts, Warranty and Who Does the Install

Both manufacturers run warranty lookups on their own sites. Rheem’s warranty page offers product registration and warranty verification; A. O. Smith runs a warranty verification page under support. Terms vary by model and by where the unit was bought, so look up your exact unit by serial number rather than trusting a warranty figure quoted in a review.

Remember too that water heater warranty coverage is mostly parts — the tank may be covered while your morning is not. Get the replacement permitted and done properly, and keep the paperwork where you will find it in year eight.

How We Pick Water Heaters

Picks here are not ranked by who pays; nobody pays to be included. They come from field experience on real jobs — which makes and mechanisms hold up in actual homes, and which ones generate callbacks — combined with published manufacturer specifications read directly from the documentation: capacity, flow rate, materials, warranty length and fit. Where it matters, picks reflect standards and code, including venting and gas-line requirements and when a job genuinely needs a licensed pro.

We weigh value rather than price, and name a small number of genuine winners instead of padding a page with every option on the market. The full method is on how we pick.

Why Trust Plumbing Picks

This site is written and reviewed by a licensed Georgia plumber — journeyman license #JP507711, verifiable through the Georgia Secretary of State. There are no paid placements and no sponsored picks; nobody buys a place on a list here. Where a link goes to Amazon, Plumbing Picks earns a commission at no extra cost to you, and that is disclosed at the top of the page. More on the license and the approach is on the about page.

Which Should You Buy?

Buy the A. O. Smith or the Rheem that matches your fuel, your venting and your capacity, and that the supply house nearest you services and stocks parts for. If both are equally available, buy the one your installer fits every week — someone who knows a platform diagnoses it faster and carries the right parts on the van. Do not pay a premium for the badge. Pay it for a better model, a better warranty on your specific unit, or a better installer.

FAQ

Are A.O. Smith and Rheem the same company? No. They are separate manufacturers competing directly. Each sells under several names: A. O. Smith’s brands page lists American, State, Reliance, Lochinvar and Takagi, while Ruud and Richmond both carry Rheem Manufacturing Company’s copyright in their own site footers.

Is one brand more reliable than the other? Not in a way that survives contact with a specific model. Water heater life tracks sizing, water chemistry, whether a thermal expansion tank was fitted and whether the anode rod was ever replaced, far more than it tracks the badge on the jacket.

Which one has the better warranty? It depends on the model, and both publish terms per unit. Rheem’s warranty page offers registration and warranty verification, and A. O. Smith runs a warranty verification page. Look up the exact unit by serial number instead of comparing brands in the abstract.

Can I install either one myself? Sometimes an electric swap; rarely a gas one. Gas venting, combustion air and gas-line sizing are code-governed and get people hurt. Check your local permit requirement before you touch it.

Does A.O. Smith or Rheem make more of the water heaters on the shelf? Between them they cover a lot of the shelf, because both sell through several badges. If you see American, State, Reliance, Lochinvar or Takagi, that is the A. O. Smith side; Ruud and Richmond are the Rheem side.

Bottom Line

A. O. Smith and Rheem are two competent, direct competitors, and either will give you a decade of hot water if the model is right and the install is right. Spend your attention on category, sizing, venting and the installer, and treat the badge as the tiebreaker it actually is. For the specific units worth buying, start at the water heater picks.

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