AO Smith Tankless Water Heater Price & Costs | AO Smith Buying Guide (2023)

How much does an AO Smith tankless water heater cost installed in your home?

AO Smith tankless water heater prices range between $600 and $3,500 for the unit alone. Professional installation will cost an additional $500 to $3,000, or more, with the average cost around $1,700. There are many factors that can affect installation costs and we detail these factors later in this post.

AO Smith Tankless Water Heater Price Overview

Model #’sFuelIndoor / OutdoorBTUs/kWUEF Range

Installed Price Range


910 ModelsNG or LPBoth380K.8 – .82$5,000-$7,500
510 ModelsNG or LPBoth199K0.8$2,500-$4,500
310 ModelsNG or LPBoth190K.81-.82$2,300-$3,200
110 ModelsNG or LPBoth140K0.8$1,500-$2,600
540 ModelsNG or LPBoth199K.93-.95$3,000-$5,300
340 ModelsNG or LPBoth180K.94-.95$2,600-$4,500
240 ModelsNG or LPBoth160K.94-.95$2,200-$3,400
140 ModelsNG or LPBoth120K.90-.91$1,600-$2,600
R4MA/R4LA -4 ChamberElectricIndoor18kW-32kW.92-.93$1,500-$4,000
R2VA -2 ChamberElectricIndoor14kW-16kW0.84$1,300-$3,500

AO Smith makes a full range of gas tankless hot water heaters including non-condensing, condensing in a variety of sizes. They also make electric tankless hot water heaters.

Pricing Sections

Below we provide full reviews of all of the AO Smith tankless hot water heaters with details on size, efficiencies, gallons per minute (GPM) flow rate, and other important features.

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Who is AO Smith

AO Smith is a leading manufacturer of residential and commercial water heaters, including tankless water heaters, boilers, and storage tanks. Many of their products are very energy efficient and are either Energy Star qualified or Energy Star certified.

AO Smith began producing residential hot water tanks in 1939 and expanded into the commercial hot water heating market in 1953. Their history actually begins in 1874 when Charles Smith founded C.J. Smith & Sons, a baby carriage and bicycle parts maker. They have made a variety of products over the years including automotive frames and bomb casings.

AO Smith is headquartered in Ashland City, Tennessee and their largest manufacturing plant, the world’s largest water heater factory, is also located there. AO Smith also has four other plants in North America, as well as in China and The Netherlands.

Overview of AO Smith Tankless Hot Water Heaters

AO Smith offers a full line of tankless hot water heaters that are fueled by gas, either natural gas or propane, and electricity. The gas units are available in non-condensing and condensing models in a variety of sizes and options.

Here we will categorize the models by gas, non-condensing, gas, condensing, and electric. First we provide some information on the AO Smith model numbers which will help clarify the type of fuel each model uses, the size of the unit, whether it requires indoor or outdoor installation, and whether the unit comes with a re-circulating pump or descaling technology.

Note on model numbers: We’ve included an explanation of AO Smith water heaters numbers below. It should prove useful as you compare AO Smith tankless units to determine which is the right one for your specific needs.

AO Smith Non-Condensing Gas Tankless Hot Water Heaters

These units are more affordable than condensing water heaters, but they are not as energy efficient with efficiencies in the low-80% range vs above 90% for condensing models.

910 Models

The 910 is a large unit with a maximum BTU level of 380K BTUs and a maximum gallons per minute (GPM) flow rate of 14.5. This unit can be installed indoors or out and is available for natural gas or propane. The 910 is capable of supplying hot water and can also be combined with hot water heating applications. It is a good choice for a large (6+ person) household and is able to supply simultaneous hot water to a variety of sources like showers, sinks, and a washing machine.

The warranty on all of the non-condensing units is exceptional with 15 years on the heat exchanger and 5 years on parts.

Maximum BTUs: 380K

Maximum GPM: 14.5

UEF: 80-82%

Installed Cost: $5,000 – $7,500

510 Models

The 510 models are good choices for medium to medium-large homes with 4 to 5 people, even in cold climates where incoming water temperatures may be below 45 degrees. These units can be used with water storage tanks and recirculation systems. Choose indoor or outdoor installation and natural gas or propane.

Maximum BTUs: 199K

Maximum GPM: 10

UEF: 81%

Installed Cost: $2,500 – $ 4,500

310 Models

The 310 models can also be installed inside or out, use natural gas or propane and will be a good fit for a two-bath home in a cold climate and up to a 4 bath home in a hot climate.

Maximum BTUs: 190K

Maximum GPM: 8

UEF: 81%

Installed Cost: $2,300 – $3,200

110 Models

The 110 models are great for smaller spaces like one-bath homes in cold climates and can also be used in cabins and summer homes.

Maximum BTUs: 140K

Maximum GPM: 6.6

UEF: 81%

Installed Cost: $1,500 – $ 2,600

AO Smith Condensing Gas Tankless Hot Water Heaters

All of AO Smith’s condensing hot water heaters are very efficient – between 91% and 95% – and are all Energy Star certified. With most of these units, the primary heat exchanger is made of commercial-grade copper and the secondary heat exchanger is made of marine-grade stainless steel. All of the condensing units hold excellent warranties with 15 years on the heat exchanger and 5 years on parts.

540 Models

There are three options with the 540 models. Choose the standard condensing unit, the condensing unit with a built-in re-circulation pump, or the condensing unit that includes scale prevention technology.

All of the 540 models are available for indoor or outdoor installation and with natural gas or propane. These units are capable of providing continuous hot water to a 4 to 5 person household even in a cold climate.

540 Standard Models

Maximum BTUs: 199K

Maximum GPM: 10

UEF: 93% – 95%

Installed Cost: $3,000 – $4,700

540 Models with Recirculating Pump

A built-in recirculating pump raises the upfront cost. But if you want recirculation, which provides faster (almost immediate) hot water at the most-used outlets, then buying a unit with that already has a pump will lower cost rather than adding a separate pump later.

Maximum BTUs: 199K

Maximum GPM: 10

UEF: 93% – 95%

Installed Cost: $3,500 – $5,300

540 Models with Scale Prevention – Model numbers that include HX3

Maximum BTUs: 199K

Maximum GPM: 10

UEF: 93 – 95%

Installed Cost: $3,300 – $5,000

340 Models

The 340 models are available either as standard condensing units or with scale prevention. These units are all suitable for a 2 bath, 4 person home in a cold climate or a 3-4 bath, 4 to 6 person home in a warm climate. Choose natural gas or propane and indoor or outdoor models.

340 – Standard Models

Maximum BTUs: 180K

Maximum GPM: 8

UEF: 94% – 95%

Installed Cost: $2,600 – $4,500

340 Models with Scale Prevention

Maximum BTUs: 180K

Maximum GPM: 8

UEF: 94% – 95%

Installed Cost: $2,900 – $4,500

240 Models

The 240 models are capable of providing hot water to a 2 bath home in northern climates and a 3 bath home in southern climates. 240 models also come in standard condensing units and units with scale prevention in either natural gas or propane and for indoor or outdoor installation.

240 – Standard Models

Maximum BTUs: 160K

Maximum GPM: 6.6

UEF: 94% – 95%

Installed Cost: $2,200 – $3,000

240 Models with Scale Prevention – Model numbers that include HX3

Maximum BTUs: 180K

Maximum GPM: 6.6

UEF: 94% – 95%

Installed Cost: $2,500 – $3,400

140 Models

The 140 models are standard condensing units and are suitable for a 1 bath home in cold climates or a 2 bath home in warm climates. These units are also a good choice for summer homes and cabins and are available for natural gas, propane, indoor, or outdoor installation.

Maximum BTUs: 120K

Maximum GPM: 6.6

UEF: 94% – 90% – 91%

Installed Cost: $1,600 – $2,600

As you can see, AO Smith makes a large lineup of gas tankless water heaters. For comparison, we have completed a comprehensive review of other leading brands like Rheem and Rinnai. Or consider our reviews of Navien and Noritz too.

A. O. Smith Gas Tankless Water Heaters and Prices
Model#FuelIndoor/ OutdoorMaximum BTUsMaximum GPMUEFEnergy Star CertifiedUnit CostUnit Cost with Pro Installation
ATIO-910-N/ATIO-910-ANNatural GasEither380K14.50.80No$3,800 – $4,000$5,000-$7,500
ATIO-910-P/ATIO-910-APPropaneEither380K14.50.82No$3,800 – $4,000$5,000-$7,500
ATI-510C-NNatural GasIndoor199K100.81No$1,200 – $1,500$2,500-$4,500
ATI-510UNat. Gas/Prop.Indoor199K100.81No$1,200 – $1,500$2,500-$4,500
ATO-510UNat. Gas/Prop.Outdoor199K100.81No$1,200 – $1,500$2,500-$4,500
ATI-310C-NNatural GasIndoor190K80.82No$900 – $1,200$2,300-$3,200
ATI-310UNat. Gas/Prop.Indoor190K80.81No$900 – $1,200$2,300-$3,200
ATO-310UNat. Gas/Prop.Outdoor190K80.81No$900 – $1,200$2,300-$3,200
ATI-110UNat. Gas/Prop.Indoor140K6.60.81No$700 – $1,100$1,500 -$2,600
ATO-110UNat. Gas/Prop.Outdoor140K6.60.81No$700 – $1,100$1,500 -$2,600
ATI-540H-NNatural GasIndoor199K100.93Yes$1,300 – $1,750$3,000-$4,700
ATO-540H-NNatural GasOutdoor199K100.95Yes$1,300 – $1,750$3,000-$4,700
ATI-540H-PPropaneIndoor199K100.93Yes$1,300 – $1,750$3,000-$4,700
ATO-540H-PPropaneOutdoor199K100.95Yes$1,300 – $1,750$3,000-$4,700
ATI-340H-NNatural GasIndoor180K80.95Yes$1,100 – $1,500$2,600-$4,500
ATO-340H-NNatural GasOutdoor180K80.94Yes$1,100 – $1,500$2,600-$4,500
ATI-340H-PPropaneIndoor180K80.95Yes$1,100 – $1,500$2,600-$4,500
ATO-340H-PPropaneOutdoor180K80.94Yes$1,100 – $1,500$2,600-$4,500
ATI-240H-NNatural GasIndoor160K6.60.95Yes$1,000 – $1,200$2,200-$3,000
ATO-240H-NNatural GasOutdoor160K6.60.94Yes$1,000 – $1,200$2,200-$3,000
ATI-240H-PPropaneIndoor160K6.60.95Yes$1,000 – $1,200$2,200-$3,000
ATO-240H-PPropaneOutdoor160K6.60.94Yes$1,000 – $1,200$2,200-$3,000
ATI-140H-NNatural GasIndoor120K6.60.90Yes$850 – $1,000$1,600-$2,600
ATO-140H-NNatural GasOutdoor120K6.60.91Yes$850 – $1,000$1,600-$2,600
ATI-140H-PPropaneIndoor120K6.60.90Yes$850 – $1,000$1,600-$2,600
ATO-140H-PPropaneOutdoor120K6.60.91Yes$850 – $1,000$1,600-$2,600

Condensing models with built-in recirculating pump:

ATI-540P-NNatural GasIndoor199K100.93Yes$1,700 – $2,000$3,500-$5,300
ATO-540P-NNatural GasOutdoor199K100.95Yes$1,700 – $2,000$3,500-$5,300
ATI-540P-PPropaneIndoor199K100.93Yes$1,700 – $2,000$3,500-$5,300
ATO-540P-PPropaneOutdoor199K100.95Yes$1,700 – $2,000$3,500-$5,300

Condensing models with descaling technology:

ATI-540HX3-NNatural GasIndoor199K100.93Yes$1,600 – $1,800$3,300-$5,000
ATO-540HX3-NNatural GasOutdoor199K100.95Yes$1,600 – $1,800$3,300-$5,000
ATI-540HX3-PPropaneIndoor199K100.93Yes$1,600 – $1,800$3,300-$5,000
ATO-540HX3-PPropaneOutdoor199K100.95Yes$1,600 – $1,800$3,300-$5,000
ATI-340HX3-NNatural GasIndoor180K80.95Yes$1,400 – $1,500$2,900-$4,500
ATO-340HX3-NNatural GasOutdoor180K80.94Yes$1,400 – $1,500$2,900-$4,500
ATI-340HX3-PPropaneIndoor180K80.95Yes$1,400 – $1,500$2,900-$4,500
ATO-340HX3-PPropaneOutdoor180K80.94Yes$1,400 – $1,500$2,900-$4,500
ATI-240HX3-NNatural GasIndoor160K6.60.95Yes$1,250 – $1,400$2,500-$3,400
ATO-240HX3-NNatural GasOutdoor160K6.60.94Yes$1,250 – $1,400$2,500-$3,400
ATI-240HX3-PPropaneIndoor160K6.60.95Yes$1,250 – $1,400$2,500-$3,400
ATO-240HX3-PPropaneOutdoor160K6.60.94Yes$1,250 – $1,400$2,500-$3,400

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AO Smith Electric Tankless Hot Water Heaters

All of the AO Smith electric tankless water heaters are made to be easily installed on the wall next to the breaker box and feature a digital display with simple “up” and “down” arrows for temperature control. Venting is not required for these units.


Chambers: 4

Maximum Wattage: 32,000

GPM at 40° temperature rise: 5.5 (2-3 person home in cold climate)

UEF: 93%

Installed Cost: $1,800 – $4,000


Chambers: 4

Maximum Wattage: 28,000

GPM at 40° temperature rise: 4.8 (2 person home in any climate)

UEF: 92%

Installed Cost: $1,700 – $3,900


Chambers: 4

Maximum Wattage: 24,000

GPM at 40° temperature rise: 4.1 (2-3 person home in moderate climate)

UEF: 92%

Installed Cost: $1,600 – $3,800


Chambers: 4

Maximum Wattage: 22,000

GPM at 40° temperature rise: 3.8 (2 person home in moderate climate)

UEF: 92%

Installed Cost: $1,500 – $3,700


Chambers: 4

Maximum Wattage: 18,000

GPM at 40° temperature rise: 3.1 (1-2 person home in cold climate)

UEF: 92%

Installed Cost: $1,500 – $3,500


Chambers: 2

Maximum Wattage: 16,000

GPM at 40° temperature rise: 2.7 (1-2 person home in moderate climate)

UEF: 84%

Installed Cost: $1,400 – $3,500


Chambers: 2

Maximum Wattage: 14,000

GPM at 40° temperature rise: 2.4 (2 person home in warm climate)

UEF: 84%

Installed Cost: $1,300 – $3,000

A. O. Smith Electric Tankless Water Heaters and Prices
Model #ChamberskW Maximum Wattage GPM at 40° temp. riseUEFEnergy Star Unit Cost w/o InstallationUnit Cost with Pro Installation
R4MA-320E432320005.50.93No$800 – $1,000$1,800-$4,000
R4LA-280E/R4LA-280X428280004.80.92No$700 – $950$1,700-$3,900
R4LA-240E424240004.10.92No$600 – $900$1,600-$3,800
R4LA-220E422220003.80.92No$600 – $850$1,500-$3,700
R4LA-180-E418180003.10.92No$550- $800$1,500-$3,500
R2VA-140E/R2VA-140X214140002.40.84No$450- $600$1,300-$3,000

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AO Smith Tankless Hot Water Heater Features

Low or Ultra Low NOx Emissions

All of the AO Smith gas tankless water heaters have low or very low NOx (nitrogen oxide) emissions making them safe for your home.

Energy Star Certified

The AO Smith condensing tankless hot water heaters are all Energy Star certified meaning they are extremely energy efficient qualifying them for utility rebate programs.

Commercial Grade Heat Exchangers

All of the 910 and 510 non-condensing units and the 340 and 540 condensing units feature a commercial grade copper primary heat exchanger. The 910, 340, and 540 all have a marine grade, stainless steel, secondary heat exchanger.

Safety Features

All units have a range of safety features including overheat and surge protection, freeze protection on the outdoor models, and they come with easy-to-read digital displays that will show troubleshooting diagnostic codes.

Scale Prevention

AO Smith’s scale prevention technology, X3™ Scale Prevention is available on the 540, 340, and 240 condensing units. X3 Scale Prevention can extend the life of the unit up to three times longer and is approved to work with an external recirculation pump and crossover valve.

High Elevation

All indoor condensing gas models are certified for up to 10,100 feet of altitude.

Factors That Affect Installation Cost

There are a number of factors that can increase the cost to install a tankless water heater including the size and type of the unit. If the unit is installed indoors, venting will be needed and if you plan to purchase a unit with a re-circulation pump or tie into an existing re-circulation system, re-plumbing may be necessary.

A new indoor system may require new gas and water lines which can be very labor intensive. Since tankless hot water tanks require electricity for ignition, a new electric outlet may be needed. Installation costs usually include removing the old tank or system.

Always get several quotes and make sure the contractor has verified experience installing these units.

Warranty Information

AO Smith warranties are only valid if the unit is used in a single-family residence and installed by an AO Smith approved contractor.

Gas Models

All of the gas tankless water heaters carry a Limited 15 year warranty on the heater exchangers and a 5 year Limited warranty on parts.

Electric Models

The electric tankless water heaters all carry a Limited 5 year warranty on the chamber and a 1 year Limited warranty on parts.

Understanding AO Smith Model Numbers

Gas Models

All of the AO Smith gas-fueled tankless hot water heaters start with ATO, ATI, or ATIO. The “O” indicates outdoor installation, the “I” indicates indoor installation, and “IO” indicates either indoor or outdoor.

Next you’ll find three numbers, 910, 540, 510, 340, 310, 240, 140 or 110. These numbers indicates maximum BTUs the unit can provide as follows:

9=380K BTUs

5=199K BTUs

3=180K BTUs

2=160K BTUs

1=140K BTUs

If the second number is a “10” the unit is a non-condensing model. If this number is “40” the unit is a condensing model.

A “P” immediately following these numbers indicates the unit includes a built-in re-circulating pump.

Some of the condensing models feature AO Smith’s X3™ Scale Prevention technology. These models include the characters “HX3” after the three numbers.

The very last letter will either be an “N” for natural gas fuel or “P” for propane. Some of the non-condensing units use the letter “U” instead of an “N” or “P”, which means the unit can be set up for either natural gas or propane.

Example Gas Model Numbers:

ATIO-910-N – This is a 380K BTU, non-condensing, natural gas unit, for either indoor or outdoor installation.

ATO-110U – This is a 140K BTU, non-condensing unit for either natural gas or propane and outdoor installation.

ATI-540P-P – This model is a 199K BTU, condensing unit with a recirculating pump that uses propane and is installed inside the home.

ATI-340HX3-N – Here’s a 180K BTU, natural gas, condensing unit for indoor installation that includes the scale prevention technology.

Electric Models

These numbers are much simpler with the 4 chamber units beginning with the characters R4MA or R4LA and the 2 chamber units beginning with R2VA. These characters are followed by 3 numbers which indicate the size of the unit in kilowatts -320, 280, 240, 220, 180, 160, and 140. The last letter will be an “E” for 240 volts or an “X” for 208 volts.

Example Electric Model Numbers

R4MA-320E – This is a 4 chamber, 32kW, 240 voltage unit.

R2VA -140X – This unit has 2 chambers, provides 14kW, and runs at 208 volts.

Where to Purchase AO Smith Tankless Hot Water Heaters

AO Smith tankless hot water heaters are available at places like Lowes and other home improvement stores. That’s a good DIY option if you know what unit will be best for your needs and have the skills to install it safely and effectively.

However, if you plan to have a contractor install the unit, then it makes sense to consult one before deciding on the model. The contractor will assist in choosing the right size and type to best fit your planned use. AO Smith tankless models are also sold and installed by local independent contractors. They’d be glad to provide you with an estimate.

Corporate Contact Details

AO Smith Water Products

500 Tennessee Waltz Parkway

Ashland City, TN 38015

Phone: 877-552-0010

Tech Support Hours:

M-F 8a – 10p EST

Weekends 9a – 6p EST

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