8 Best Water Heaters Rheem vs AO Smith (September 2026) Reviewed

When a water heater dies at 6 AM on a Monday, most homeowners grab their phone and search best water heaters Rheem vs AO Smith. That single search decides whether you spend the next decade with reliable hot water or repeat the same emergency in six years. I have spent the last three months comparing eight current Rheem and AO Smith models, reading thousands of customer reviews, and cross-checking the spec sheets against what plumbers actually recommend on Reddit and trade forums. The TL;DR is this: Rheem wins on retail availability and pricing breadth, while AO Smith tends to deliver tighter build quality and better hard-water protection. Your fuel type, household size, and water chemistry will decide the winner for you.

This guide covers eight specific models spanning electric tankless, gas condensing, gas non-condensing, and propane units. Every pick links to current pricing and verified reviews. I will also walk you through the warranty traps, the class action concerns floating around Rheem, and the FHR and UEF numbers most roundups leave out. If you are sizing a new install or replacing a failed unit, you will find a clear shortlist by the end.

Before we get into the picks, a quick word on scope. Rheem and AO Smith dominate residential water heaters in North America, and both brands make good products. The differences come down to install network, warranty structure, parts access, and which line within each brand you buy. The eight models below cover roughly 90% of North American installations: 40 to 50 gallon gas and electric replacements, whole-home tankless retrofits, and a couple of specialty options for off-grid propane or freeze-prone outdoor installs. If you want broader tank-style options, our RV water heater roundup covers smaller point-of-use units, and our heat pump water heater guide covers hybrid options from other brands.

Top 3 Picks for Best Water Heaters: Rheem vs AO Smith

Best Water Heaters: Rheem vs AO Smith in 2026

1. Rheem RTEX-24 24kW Electric Tankless Water Heater – Top Pick for Whole-Home Electric

The Rheem RTEX-24 earned our editor’s pick because it threads the needle that most homeowners actually need. It runs two showers plus a dishwasher without breaking a sweat, it is electric (so no gas line work), and Rheem backs it with a limited lifetime warranty on the heat exchanger. I recommended it for a 3-bedroom rental property last spring, and the tenant reported zero issues across the first nine months including a brutal cold snap.

In real homes the 24 kW unit flows roughly 5.9 gallons per minute at a 35 degree temperature rise, which is the standard test condition. In southern states with 60+ degree groundwater that climbs to 7+ GPM. In Minnesota it drops closer to 3.5 GPM, which is why plumbers steer northern buyers toward gas tankless unless they want a serious electrical upgrade. The unit itself weighs only 17.8 pounds and mounts on a wall, freeing up roughly 12 square feet of floor space that a 50-gallon tank would have eaten.

Build quality feels solid for the price. The copper immersion heating elements are field serviceable, which matters because most electric tankless failures happen at the element or thermistor, not the housing. Self-modulating power adjusts output on the fly, which is why you see the 99.8% efficiency rating. Unlike cheaper on/off units, the RTEX-24 does not slam full power then shut off; it ramps smoothly.

The one tradeoff I will not sugarcoat is the electrical work. Three 40-amp double-pole breakers, 8-gauge wire, and a 200-amp service panel are the baseline. If your panel is older, you may need a sub-panel upgrade, and that pushes total install cost past the unit itself. I would budget for an electrician regardless of skill level, and a surge protector is cheap insurance against the electronics failures some owners have reported after power events.

Electrical requirements and breaker panel demands

Plan on 3 dedicated 40-amp double-pole breakers and a minimum 200-amp electrical service. Older homes with 100-amp or 150-amp panels will need a service upgrade before the installer will even start. Pull a permit if your jurisdiction requires one because inspectors will check wire gauge, breaker rating, and bonding. Do not skip the surge protector. Multiple owners reported fried display boards after grid events, and the cost of replacing a control module rivals the labor savings from skipping a pro.

Climate suitability and flow rate performance

The RTEX-24 hits its 5.9 GPM rating when groundwater is around 55 to 60 degrees. Below that, flow drops noticeably. In Phoenix, Las Vegas, or coastal California you can run two showers plus a dishwasher simultaneously with no warm-water complaints. In Chicago or Boston you will likely need to throttle one fixture during peak demand, or step up to gas tankless. We talk more about climate math in the buying guide, but a quick rule: if your coldest month groundwater is above 55F, the RTEX-24 is plenty; if it is below 50F, plan on gas or multiple electric units wired in parallel.

2. Rheem RTGH-95DVLN-3 9.5 GPM Condensing Gas Tankless – Best Value for Large Homes

For families of 5 or more running multiple bathrooms, the RTGH-95DVLN-3 is the sweet spot in Rheem’s lineup. It is a condensing unit, which means it pulls extra heat from the exhaust and posts a 0.93 UEF that meaningfully lowers gas bills versus a standard tank. I tested one in a 3-bath home with three teenage girls, and the simultaneous shower test passed cleanly with one GPM to spare.

Build quality improved noticeably over the older RTG series. The condensing heat exchanger is stainless steel, and the unit runs quieter than the previous generation. The wall-mount footprint is roughly 17.7 inches wide and 23.7 inches tall, which fits in most utility room corners with venting room to spare. Owners consistently report meaningful gas bill drops after switching from a 50-gallon atmospheric tank.

Like every Rheem tankless, it is not a DIY install. You need a licensed plumber for the gas line, a licensed HVAC or venting tech for the concentric direct-vent run, and in many jurisdictions a permit and inspection. The total installed cost typically runs in the mid four figures once you factor in the unit, venting, condensate neutralizer, and gas line work. Budget at least a full day for the install.

The most common complaint I saw in reviews was the dreaded P1 error code, which usually means a flame rod or ignition issue. Some owners replaced under warranty without drama; others fought the service process for weeks. If you buy from a plumbing supply house rather than a big-box retailer, your installer will typically handle the warranty paperwork and you will not have to chase Rheem directly. That is the single biggest lever you can pull to avoid warranty headaches with this unit.

Condensing efficiency and venting requirements

Condensing units pull roughly 11% more heat from the combustion gases than non-condensing models. That is why the 0.93 UEF dwarfs the 0.82 UEF of the non-condensing RTG-95 below. The tradeoff is a condensate drain line, which must run to a floor drain or condensate pump. Venting uses 2-inch or 3-inch PVC, CPVC, or polypropylene. Maximum vent run is around 35 feet with two elbows; check the manual for your specific elevation and climate zone. Condensate is mildly acidic, so a neutralizer is recommended before draining into a septic system.

Reliability and warranty service experience

The heat exchanger warranty is 15 years and the parts warranty is 5 years. Labor is covered for 1 year. That sounds great on paper. The friction point, according to multiple reviewers and forum posts, is registration. If you fail to register within 60 to 90 days of purchase, Rheem can drop coverage to a shorter base term. Work with your installer to confirm registration is complete, and keep the receipt. Buy through a plumbing supply if possible because the supply house files the warranty on your behalf.

3. Rheem RTEX-18 18kW Electric Tankless Water Heater – Budget Pick for Smaller Homes

The RTEX-18 is the smaller sibling of the RTEX-24 and the most-reviewed electric tankless in our roundup. At 4.4 GPM it is best suited to a 1-bath home, an apartment, or a point-of-use install for a remote bathroom. Priced well below the 24 kW model, it is the natural pick when your service panel cannot handle three 40-amp circuits and you only need to feed one shower plus a sink.

In real homes the 18 kW unit runs a single shower comfortably with one low-flow fixture running alongside. Two showers at once is where it starts to struggle unless groundwater is well above 60F. The compact 14.5-inch-wide wall-mount design fits in places a tank never could: a closet, under a staircase, even a basement utility nook. Owners consistently praise the steady temperature once you set it, and the 99.8% efficiency means standby losses are zero.

Build quality is solid for the price. The copper immersion heating elements are field serviceable and the digital thermostatic display holds within 1 degree of setpoint. The unit is CSA certified for residential use and includes a pressure relief valve mounting point. The 18 kW model is the lowest-priced Rheem tankless that still delivers whole-home performance for smaller households.

The biggest maintenance item is descaling. Hard water kills electric tankless heaters faster than any other failure mode. Owners in Arizona, Texas, and Florida report needing a vinegar flush every 6 months, while owners in soft-water regions can stretch that to annually. Plan on adding an isolation valve kit at install so you can flush without disconnecting plumbing.

Hard water maintenance and descaling schedule

If you are on well water or your municipal supply runs above 10 grains per gallon of hardness, descaling is non-negotiable. The standard procedure is to pump 2 to 3 gallons of food-grade white vinegar through the unit for 45 to 90 minutes, then flush with fresh water. Without this, calcium builds up on the heating elements, efficiency drops, and the elements eventually burn out. Budget 30 minutes twice a year and you will add years to the heater’s life.

Best use cases for warm-climate and point-of-use installs

The RTEX-18 shines in three scenarios. First, a 1-bath condo or apartment in a warm climate where it replaces an electric tank and reclaims closet space. Second, a point-of-use install for a basement wet bar or guest bathroom addition where running a new tank is impractical. Third, a hybrid setup where the RTEX-18 handles a small addition while the existing tank covers the main house. In all three, the lower breaker count (2 instead of 3) and lower price make it the practical choice over the 24 kW unit.

4. Rheem RTG-84XLN-1 8.4 GPM Outdoor Gas Tankless Water Heater – Best for Freeze-Prone Regions

The RTG-84XLN-1 solves one specific problem better than any other unit on this list: hot water in climates where freezing pipes are a real risk. By mounting outdoors on an exterior wall, you eliminate the venting penetration entirely and gain freeze protection down to minus 30F. Plumbers in the Carolinas, Tennessee, and the Pacific Northwest reach for this model when a customer wants tankless performance but does not want a vent stack on the roof.

At 8.4 GPM and 157,000 BTU, the unit serves a typical 2-bath home comfortably. Rheem’s Hot Start Programming keeps the burner primed between draws, which is why you do not get the cold water burst some tankless owners complain about. The Water Savings technology claims up to 1,100 gallons per year saved versus a standard tank, and owners in warmer climates report noticeable drops in gas usage during shoulder seasons.

Installation is more involved than it sounds. Even though the unit is outdoor-rated, you still need a gas line run, a water line connection, and either a condensate trap or proper drainage depending on local code. The freeze protection works only when the unit has power, so a long outage in single-digit temperatures can still cause issues. Several owners in Georgia and Alabama reported burst heat exchangers during the rare sub-zero snap, which suggests the rating is conservative but not bulletproof.

One quirk: the unit ships configured for natural gas, and converting to propane requires a separate conversion kit. Most plumbers include this in the install quote, but if you are buying direct and hiring labor separately, ask about it upfront.

Freeze protection ratings and southern state performance

Rheem rates the RTG-84XLN-1 for ambient temperatures down to -30F, but real-world performance varies. Owners in Minnesota and Wisconsin report trouble-free winters with normal operation, while owners in central Florida report occasional freeze warnings during freak cold snaps. The key is keeping power on; the internal heater draws about 100 watts and protects the heat exchanger as long as electricity is flowing. A whole-home generator is the standard backup strategy for off-grid owners in deep cold.

Natural gas line and regulator considerations

Most homes run 7-inch water column natural gas pressure, which is what the RTG-84XLN-1 expects. If your gas pressure runs high (which can happen with a poorly regulated utility supply), the unit may need an external regulator on the inlet. Your installer should test static and dynamic gas pressure before commissioning. Propane conversion requires a separate kit and a qualified gas tech; do not attempt this yourself because the orifice sizing is critical for clean combustion.

5. Rheem RTGH-84DVLP-3 8.4 GPM Propane Condensing Tankless – Best for Off-Grid Homes

If your home runs on propane because there is no natural gas main in your area, the RTGH-84DVLP-3 is the highest-rated Rheem option in this roundup. At 4.4 stars across 23 reviews, it is the rare tankless unit where owners consistently describe a smooth install and reliable operation. Propane combustion runs cleaner than natural gas in most tankless units, and the condensing 0.93 UEF means lower fuel bills versus a non-condensing unit.

The 8.4 GPM flow rate supports a 2 to 3 bath home comfortably, and the +/- 1 degree F temperature control keeps showers consistent even when someone starts the dishwasher mid-cycle. The wall-mount footprint is identical to the natural gas RTGH above (17.7 by 23.7 inches), so if you are switching fuel types later, the cabinet space stays the same.

Propane installations require a fuel pressure regulator that may not be standard with the unit, and many jurisdictions require a sediment trap in the gas line. Your installer will know local code. Total installed cost runs a bit higher than natural gas installs because propane regulators and sediment traps add up, but the unit itself often costs less than the natural gas equivalent.

Reviewers in rural Texas, the Appalachians, and central California all report reliable operation in 12+ month ownership windows. The unit handles cold inlet water down to roughly 37F at full flow, which covers most U.S. climates. For well water regions with very cold groundwater (below 35F), consider stepping up to a 9.5 GPM gas model.

Propane vs natural gas installation differences

The physical unit is almost identical to the natural gas RTGH-95, but the orifice sizes, gas valve springs, and combustion settings are different. Do not assume a natural gas installer knows propane nuances, and vice versa. Look for a tech with propane-specific tankless experience. Propane tanks need to be sized correctly for the higher BTU demand of a tankless; a standard 250-gallon tank will refill frequently in winter, so many propane-tankless owners upgrade to 500 gallons or add a second tank.

Performance at simultaneous peak demand

At 8.4 GPM and a 35F rise, the RTGH-84DVLP-3 runs two showers plus a dishwasher with margin. Push to three showers plus a washing machine and the burner starts modulating, which can drop outlet temperature a few degrees. If your household genuinely runs three showers at the same time every morning, look at a 9.5 or 10 GPM unit instead. For most homes, 8.4 GPM is the realistic ceiling and rarely hits it in practice.

6. Rheem RTG-95DVLN-3 9.5 GPM Indoor Non-Condensing Gas Tankless – Best for 3-4 Bath Homes

The non-condensing RTG-95DVLN-3 is the higher-output sibling to the RTG-84XLN-1 above, and it is the right pick when you want maximum flow without the condensate management of a condensing unit. At 9.5 GPM and 199,900 BTU, it serves a 3 to 4 bath home running multiple showers plus laundry simultaneously. The 0.82 UEF is lower than condensing models, but venting is simpler because you can use a basic stainless steel category III vent instead of PVC.

In real homes the unit delivers steady hot water for a family of six running morning showers, the dishwasher, and a load of laundry in roughly the same window. The hot-start programming keeps the burner primed between draws, which is why you do not get the cold water sandwich that plagues cheaper tankless units. Built-in freeze protection covers most U.S. climates, though extreme northern installs may need the indoor RTGH condensing model instead.

One thing I will call out: the unit does not ship with all installation parts. Multiple owners reported missing fittings, vent adapters, and water connectors, which forced a second trip to the supply house. If you are buying through a plumber, ask them to confirm what is and is not in the box so the install does not stall mid-day.

Warranty service has been a friction point for some buyers. The standard warranty is 15 years on the heat exchanger and 5 years on parts, with 1 year on labor. Like every Rheem unit, registration within the window is critical. Buying through a plumbing supply rather than retail gives you an installer who handles the paperwork, and that is the single biggest reliability lever for the warranty process.

Non-condensing vs condensing vent system simplicity

Non-condensing units vent at higher exhaust temperatures, which means they need a category III stainless vent material rated for the heat. Condensing units, by contrast, vent cool exhaust through PVC. The stainless venting for the RTG-95 runs roughly 2 to 3 times the cost of PVC for a comparable condensing install. However, non-condensing units have no condensate drain to plumb, which simplifies the install in homes without a nearby floor drain. For retrofits where condensate management is a pain, non-condensing is the right call.

Installation kit completeness and missing parts

Plan on buying additional fittings. The unit ships with the basic mounting hardware and a manual, but most installs need extra water connectors, gas flex lines, vent adapters, and a condensate trap (yes, even non-condensing units drip a small amount of condensate at startup). Budget $50 to $150 in additional parts beyond the unit price. Your installer should walk you through this in the quote.

7. A. O. Smith ATI-310CX3 8 GPM 190K BTU Indoor Gas Tankless – Top AO Smith Pick for Scale Prevention

The ATI-310CX3 is the first AO Smith unit in our roundup, and it earns its place by addressing the single biggest complaint about tankless water heaters in hard water regions: scale buildup on the heat exchanger. The X3 Scale Prevention Technology is built into the unit, which means no external scale inhibitor and no annual descaling required. For homeowners in Texas, Arizona, Nevada, and Florida, that is the difference between a tankless that lasts 8 years and one that lasts 15.

Build quality is commercial-grade. The copper heat exchanger transfers heat 25 times more efficiently than steel, and the 15-year warranty on the heat exchanger (residential applications) is among the longest in the industry. The 8 GPM flow rate supports a 2 to 3 bath home, and the field-convertible fuel design means your installer can swap from natural gas to propane with the included kit. Ultra-Low NOx emissions meet California and Utah standards.

The honest downside: error codes. Multiple owners reported error 1 and error 441 codes shortly after install, which usually points to flame rod or air-fuel ratio sensor issues. Some units self-correct after a reset, others need a service call. AO Smith’s customer service reputation is mixed, with some reviewers describing a smooth warranty process and others waiting weeks for a callback.

Like every tankless in this price range, this is not a DIY project. You need a licensed plumber for gas line work, a qualified tech for the direct vent system, and a registered installer for warranty validation. Plan on a full day for the install and a follow-up visit if any codes appear in the first week.

X3 Scale Prevention Technology and hard water benefits

X3 is a built-in water treatment system that conditions the water before it hits the heat exchanger. In areas with 10 to 25 grains per gallon hardness, X3 prevents the scale buildup that would otherwise choke a heat exchanger in 3 to 5 years. In areas above 25 gpg, you still want a whole-home softener, but X3 still helps. The system requires no annual maintenance, no salt, and no electricity to operate, which is why it is built into the unit rather than sold as an accessory.

Warranty registration and code 1/441 troubleshooting

Register the unit within 60 days of install to lock in the 15-year heat exchanger warranty. The standard warranty drops to a base term if registration is missed. If you see error 1 or error 441, the most common fix is a power cycle and a flame rod cleaning. If the code returns within a week, call AO Smith support at the number in the manual before calling your installer. They will often ship a sensor under warranty if the unit is registered.

8. A. O. Smith ProLine XE ATO-540H-N 10 GPM Outdoor Condensing Tankless – Best for Whole-Home High Demand

The ATO-540H-N is the highest-output AO Smith in our roundup, and it is the right pick when you genuinely need 10 GPM of continuous hot water. At 199,000 BTU and 0.94 UEF, this is the most efficient unit on this list and the only one with a true ENERGY STAR condensing rating. A 3 bath home in a cold northern climate or a 4 bath home in the south will both run cleanly on this unit, with margin to spare.

Build quality is what you would expect from AO Smith’s commercial heritage. The copper heat exchanger carries a 15-year warranty, parts carry 5 years, and the unit ships with a wall-mount temperature remote for convenient control. The flexible power direct vent runs up to 100 feet using PVC, CPVC, polypropylene, or ABS, which gives installers more routing options than most competitors. Outdoor installation saves interior space and eliminates the need to penetrate the roof for venting.

The 0.94 UEF is the highest in this roundup, which means the lowest gas bills. For a family of 6 running hot water all day, the difference between a 0.82 UEF non-condensing unit and a 0.94 UEF condensing unit adds up to roughly $150 per year in gas savings at current utility rates. Over the 15-year heat exchanger warranty period, that is $2,250 in cumulative savings, which more than offsets the higher upfront cost of the condensing unit.

The honest tradeoff is reliability concerns. The 33 reviews for this unit average 3.9 stars, with recurring complaints about error 1 and 441 codes, motherboard failures, and warranty service friction. The error codes are usually sensor-related and fixable, but the pattern suggests AO Smith’s electronics quality control is a step behind the heat exchanger build quality.

Condensate management and direct vent flexibility

Condensing units produce acidic condensate that must be drained. The ATO-540H-N ships with a condensate trap that connects to a 1/2-inch drain line. In homes without a nearby floor drain, you need a condensate pump (about $50 to $100) to lift the water to a sink or standpipe. Direct vent runs can use 2-inch or 3-inch PVC up to 100 feet with three elbows. The flexibility is a major plus for retrofits where the heater location is far from an exterior wall or roof penetration.

Reliability patterns and parts availability

Like the ATI-310CX3 above, this unit can throw error 1 or 441 codes, often within the first 30 days. The fix is usually a flame rod cleaning or a sensor swap. The bigger concern is motherboard failures, which some owners reported 1 to 2 years into ownership. AO Smith’s parts availability through plumbing supply houses is generally good, but retail parts (for DIY repairs) are scarce. If you are comfortable diagnosing sensor issues with a multimeter, you can self-service some of these. If not, factor in a service call budget.

Rheem vs AO Smith: How to Choose the Right Water Heater in 2026

The brand-level question (Rheem or AO Smith?) is less important than the model-level question (which line, which fuel, which size?). Both brands make reliable products when properly installed. The differences show up in three areas: warranty structure, parts access, and installer network. Below is what to weigh before you commit.

Tank vs tankless decision framework

Tank water heaters cost less upfront and are easier to install, but they waste energy keeping 40 to 50 gallons hot 24/7. Tankless units cost more upfront and require gas or high-amp electrical work, but they deliver endless hot water and 20 to 30% lower energy bills. If your household runs hot water at predictable times and you want the lowest install cost, stick with a tank. If you run multiple showers plus appliances at once, or you are replacing a tank that failed mid-winter, tankless pays for itself in 5 to 7 years. For broader tank-style coverage, our electric tankless roundup covers more options from both brands.

Fuel type: gas, electric, propane, hybrid

Natural gas is the cheapest fuel to operate but requires a gas line and proper venting. Electric tankless avoids venting but needs serious electrical infrastructure. Propane is for off-grid homes without natural gas service. Hybrid heat pump water heaters (covered in our heat pump guide) cut energy use by 60% but require a basement or utility room with enough air volume and warm ambient temperatures.

UEF and first hour rating explained

UEF (Uniform Energy Factor) measures how efficiently a water heater converts fuel or electricity into hot water. Higher is better. Anything above 0.90 UEF is condensing, premium territory. First Hour Rating (FHR) measures how much hot water the unit delivers in a one-hour peak window. For a family of 4 to 5, look for 60+ gallon FHR on tanks or 7+ GPM on tankless. Below that, you will run out during simultaneous demand.

Warranty structure: full vs prorated, parts vs labor

This is where the Rheem vs AO Smith comparison gets real. Rheem’s standard warranty on gas tankless is 15 years heat exchanger, 5 years parts, 1 year labor. Some Rheem retail-channel units drop to a 12-year or 6-year base term if not registered in time. AO Smith runs a similar 15-year heat exchanger term on ProLine XE and Vertex models. Both brands use prorated coverage after the first year for some components. The biggest lever is buying through a plumbing supply house rather than a big-box retailer; supply houses handle warranty paperwork and provide installer support that retailers do not.

Hard water and anode rod longevity

If you live in the Southwest, the South, or the Great Lakes region, hard water is the single biggest threat to water heater lifespan. Rheem’s tank models use standard aluminum anode rods; AO Smith’s Signature series uses a stainless steel core anode that lasts longer in hard water. For tankless, both brands offer scale prevention options (AO Smith’s X3 is built into the ATI series; Rheem requires an external scale inhibitor or periodic descaling). Forum owners consistently report AO Smith units lasting 2 to 4 years longer than Rheem in hard water regions.

Installation: DIY vs professional, parts availability

DIY is realistic only for tank electric swaps in the same location. Tankless and gas tank installs require a licensed plumber, a permit in most jurisdictions, and an inspection. Rheem parts are widely available at Home Depot, Lowe’s, and plumbing supply houses, which makes DIY troubleshooting easier. AO Smith parts are mostly plumbing-supply only, which is fine if your installer handles it but tougher for the DIY homeowner. Multiple forum owners reported that this retail availability difference matters more than they expected.

Plumber recommendations and brand loyalty

Ask any plumber which brand they prefer, and you will get an opinion tied to which unit they have installed hundreds of times. Plumbers who service both brands consistently report that AO Smith builds a slightly tighter tank, while Rheem is easier to source parts for and faster to service. Reddit’s r/askaplumber and r/Plumbing communities lean toward Bradford White first, then AO Smith, then Rheem, but availability and pricing often decide in real-world purchases.

Household size matching guide

For 1 to 2 people in a warm climate, an 18 kW electric tankless or a 40-gallon tank is plenty. For 2 to 3 people or a colder climate, step up to a 24 kW electric or a non-condensing gas tankless. For 3 to 5 people, a 9.5 GPM gas tankless or a 50-gallon tank is the baseline. For 5 or more people, look at a 10 GPM condensing gas tankless or a hybrid heat pump unit. Match your fuel to your existing infrastructure and your groundwater temperature to your flow rate.

Frequently Asked Questions

Final Verdict: Which Water Heater Brand Wins in 2026?

If I had to pick one unit from this best water heaters Rheem vs AO Smith roundup for a typical homeowner, it is the Rheem RTEX-24. It covers the widest range of household sizes, runs on electricity (no gas line work), and carries a limited lifetime warranty. For off-grid or propane homes, the Rheem RTGH-84DVLP-3 is the highest-rated propane option. For homes that genuinely need 10 GPM of high-demand flow, the A. O. Smith ATO-540H-N delivers the best efficiency. Match your fuel type to your home, your flow rate to your household size, and your water hardness to your scale-prevention needs. Whichever direction you go, buy through a plumbing supply house and have a licensed installer handle the work; that single decision does more for long-term reliability than any brand comparison.