Whole House Tankless Water Heaters

Select Product Type

Filter By

Best Selling▼

Best Selling
Price: Low to High
Price: High to Low
Name: A-Z
Name: Z-A
Recommends Only
Closeouts Only
In-stock Only
Next Day Air Only
Availability

Filters

Brand

A.O. Smith (39)

State Water Heaters (12)

Takagi (38)

Rinnai (31)

Noritz (52)

Eemax (4)

Rheem Tankless (33)

Bosch Thermotechnology (6)

GE Appliances (3)

+ Show More

Fuel Type

To create heat, some form of fuel is required. Fuel Type specifies what the product uses as an input to create heat.

Electric (7)

Liquid Propane (94)

Natural Gas (117)

Maximum Input Capacity (BTU)

The Maximum Input Capacity describes how quickly the appliance will use fuel when delivering it's maximum capacity. The units may change depending on the fuel being used.

120000 - 129999 (22)

130000 - 139999 (3)

140000 - 149999 (6)

150000 - 159999 (11)

160000 - 169999 (31)

180000 - 189999 (60)

190000 - 199999 (78)

+ Show More

Uniform Energy Factor

Uniform Energy Factor (UEF) is a measurement of water heater energy efficiency. The higher the energy factor, the more efficient the water heater.

0.80 (2)

0.81 (35)

0.82 (13)

0.83 (2)

0.84 (1)

0.85 (1)

0.88 (3)

0.89 (10)

0.90 (11)

0.91 (15)

0.92 (11)

0.93 (29)

0.94 (28)

0.95 (32)

0.96 (9)

0.97 (9)

+ Show More

Vent Type

Products that use combustion (burning) of fuel to create heat also create potentially dangerous gasses that need to be exhausted (AKA "Vented"). Depending on the product, venting can be done via a chimney, through a side wall, or use a second vent to provide fresh air to the appliance.

Concentric Vent (14)

Direct Vent (96)

Outdoor (No Venting) (99)

Power Vent (2)

Combustion Type

Condensing appliances use leftover thermal energy from combustion gases to heat water in a secondary heat exchanger, resulting in higher efficiency and lower exhaust temperature.

Condensing (151)

Non-Condensing (60)

Installation Location

Indoor (107)

Indoor / Outdoor (12)

Outdoor (99)

Gas Conversion Kit

Included (19)

Not Available (192)

Product Line

Classic Plus (12)

ecoTough (14)

Greentherm (6)

HomeAdvantage II (4)

Luxury Series (9)

Prestige (21)

ProLine XE (36)

ProTough (4)

Residential (31)

Sensei (9)

Ultra Series (3)

Value Series (10)

valueSolutions (4)

+ Show More

Voltage (Volts)

120 (188)

240 (7)

Ultra Low NOx Emissions

NOx is a byproduct of the combustion process, and it's output is regulated in some jurisdictions. Many regulators mirror SCAQMD rules, which regulate air quality for some parts of Southern California. Ultra Low NOx appliances emit less than 10-14 ng/J (nanogram per Joule) of NOx. Learn More

No (4)

Yes (200)

Flow Rate at 40F Temperature Rise (GPM)

Flow rate measures how much hot water your heater can deliver. Click Learn More to determine the appropriate temperature rise to use based on your location. Learn More

3 (1)

4 (4)

5 (22)

6 (35)

7 (36)

8 (58)

9 (55)

10 (2)

+ Show More

Flow Rate at 50F Temperature Rise (GPM)

Flow rate measures how much hot water your heater can deliver. Click Learn More to determine the appropriate temperature rise to use based on your location. Learn More

2 (1)

3 (6)

4 (27)

5 (15)

6 (112)

7 (50)

8 (2)

+ Show More

Flow Rate at 60F Temperature Rise (GPM)

Flow rate measures how much hot water your heater can deliver. Click Learn More to determine the appropriate temperature rise to use based on your location. Learn More

2 (2)

3 (29)

4 (18)

5 (114)

6 (52)

Flow Rate at 70F Temperature Rise (GPM)

Flow rate measures how much hot water your heater can deliver. Click Learn More to determine the appropriate temperature rise to use based on your location. Learn More

1 (1)

2 (6)

3 (35)

4 (118)

5 (53)

Includes Pump

No (192)

Yes (23)

Price

300 - 499 (3)

500 - 699 (13)

700 - 899 (26)

900 - 1099 (36)

1100 - 1299 (51)

1300 - 1499 (25)

1500 - 1699 (39)

1700 - 1899 (18)

1900 - 2099 (5)

2300+ (2)

+ Show More

Energy Factor

Energy Factor (EF) is a measurement of water heater energy efficiency. The higher the energy factor, the more efficient the water heater. Learn More

0.82 (1)

0.99 (5)

1 (1)

AFUE (%)

AFUE (Annual Fuel Utilization Efficiency) measures the efficiency of combustion equipment over the entire heating season, and is calculated by dividing the amount of energy that is actually heating your home by the total energy contained in the fuel used by the boiler/furnace. Learn More

98 (4)

Thermal Efficiency (%)

85 (2)

Learn More About A.O. Smith ATO-540HX3-P

A.O. Smith X3 - 6.2 GPM at 60° F Rise - 0.95 UEF - Propane Tankless Water Heater - Outdoor

Model: ATO-540HX3-P

EnergyStar Condensing Water Heater. Ultra-Low NOx (14 ng/J or 20 ppm). Ratings: 9.5 GPM at 40° F Rise, 7.5 GPM at 50° F Rise, 6.2 GPM at 60° F Rise, 5.2 GPM at 70° F Rise. 199k Max BTU/h.

Write A Review

$1,558.00

In-Stock

Free Shipping

*This product qualifies for Free Shipping anywhere in the contiguous US. Accessories may ship separately. Items over 100lbs shipped via semi-truck, be sure to select "Lift Gate" to lower the product to the ground curbside. Remote area surcharges may apply, see our full shipping policy for more details.

2% Check Discount

Save 2% instantly by using our convenient "e-check" option or by simply mailing us a paper check. Yes, your order will be delayed slightly (5 business days). But, if you can wait, the savings are significant.