Shipping Crate Icon
Free Shipping On Orders Over $199
Welcome:  Sign In | Contact Us
Call Us: (855)-436-0140
Home » » »

A.O. Smith Tankless Water Heaters

Quick Search
Plus Icon
Loading Image
A.O. Smith is one of the most trusted names in tankless water heaters, offering a wide selection for both residential and commercial applications. Find your perfect A.O. Smith tankless water heater here.
Filter ▼
Model Number ATI-540H-P is the Number 1 Seller
Learn More About ATI-540H-P
A.O. Smith
ATI-540H - 6.3 GPM at 60° F Rise - 0.93 UEF - Propane Tankless Water Heater - Direct Vent
Model: ATI-540H-P
30% Buy This
5.0 out of 55.0 out of 55.0 out of 55.0 out of 55.0 out of 5(10)
Ask a Question
$1,150.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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 Icon
2% Check Discount
Learn More About 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.
Add To Cart
Model Number ATI-340H-N is the Number 2 Seller
Learn More About ATI-340H-N
A.O. Smith
ATI-340H - 5.7 GPM at 60° F Rise - 0.95 UEF - Gas Tankless Water Heater - Direct Vent
Model: ATI-340H-N
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 8.0 GPM at 40° F Rise, 6.8 GPM at 50° F Rise, 5.7 GPM at 60° F Rise, 4.8 GPM at 70° F Rise. 171k Effective BTU/h.
22% Buy This
4.9 out of 54.9 out of 54.9 out of 54.9 out of 54.9 out of 5(10)
Ask a Question
$995.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Model Number ATI-140H-N is the Number 3 Seller
Learn More About ATI-140H-N
A.O. Smith
ATI-140H - 3.8 GPM at 60° F Rise - 0.90 UEF - Gas Tankless Water Heater - Direct Vent
Model: ATI-140H-N
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 5.4 GPM at 40° F Rise, 4.4 GPM at 50° F Rise, 3.8 GPM at 60° F Rise, 3.2 GPM at 70° F Rise. 112k Effective BTU/h.
13% Buy This
4.9 out of 54.9 out of 54.9 out of 54.9 out of 54.9 out of 5(10)
Ask a Question
$730.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Model Number ATI-540H-N is the Number 4 Seller
Learn More About ATI-540H-N
A.O. Smith
ATI-540H - 6.3 GPM at 60° F Rise - 0.93 UEF - Gas Tankless Water Heater - Direct Vent
Model: ATI-540H-N
9% Buy This
4.8 out of 54.8 out of 54.8 out of 54.8 out of 54.8 out of 5(14)
Ask a Question
$1,150.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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 Icon
2% Check Discount
Learn More About 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.
Add To Cart
Model Number ATI-240H-N is the Number 5 Seller
Learn More About ATI-240H-N
A.O. Smith
ATI-240H - 5.0 GPM at 60° F Rise - 0.94 UEF - Gas Tankless Water Heater - Direct Vent
Model: ATI-240H-N
9% Buy This
4.9 out of 54.9 out of 54.9 out of 54.9 out of 54.9 out of 5(10)
Ask a Question
$895.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATO-510-P
A.O. Smith
ATO-510 - 5.5 GPM at 60° F Rise - 0.80 UEF - Propane Tankless Water Heater - Outdoor
Model: ATO-510-P
EnergyStar Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 8.3 GPM at 40° F Rise, 6.9 GPM at 50° F Rise, 5.5 GPM at 60° F Rise, 4.8 GPM at 70° F Rise. 163k Effective BTU/h.
9% Buy This
Write a Review
Ask a Question
$959.00
Factory-Direct
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATI-140H-P
A.O. Smith
ATI-140H - 3.8 GPM at 60° F Rise - 0.90 UEF - Propane Tankless Water Heater - Direct Vent
Model: ATI-140H-P
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 5.4 GPM at 40° F Rise, 4.4 GPM at 50° F Rise, 3.8 GPM at 60° F Rise, 3.2 GPM at 70° F Rise. 112k Effective BTU/h.
4% Buy This
5.0 out of 55.0 out of 55.0 out of 55.0 out of 55.0 out of 5(8)
Ask a Question
$730.00
Factory-Direct
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATI-510-N
A.O. Smith
ATI-510 - 5.5 GPM at 60° F Rise - 0.80 UEF - Gas Tankless Water Heater - Power Vent
Model: ATI-510-N
EnergyStar Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 8.3 GPM at 40° F Rise, 6.9 GPM at 50° F Rise, 5.5 GPM at 60° F Rise, 4.8 GPM at 70° F Rise. 163k Effective BTU/h.
4% Buy This
4.8 out of 54.8 out of 54.8 out of 54.8 out of 54.8 out of 5(6)
Ask a Question
$959.00
Only 1 In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATI-540P-N
A.O. Smith
ATI-540P - 6.3 GPM at 60° F Rise - 0.93 UEF - Gas Tankless Water Heater - Direct Vent
Model: ATI-540P-N
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 9.5 GPM at 40° F Rise, 7.5 GPM at 50° F Rise, 6.3 GPM at 60° F Rise, 5.4 GPM at 70° F Rise. 189k Effective BTU/h.
4.9 out of 54.9 out of 54.9 out of 54.9 out of 54.9 out of 5(8)
Ask a Question
$1,299.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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 Icon
2% Check Discount
Learn More About 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.
Add To Cart
Learn More About ATI-540P-P
A.O. Smith
ATI-540P - 6.3 GPM at 60° F Rise - 0.93 UEF - Propane Tankless Water Heater - Direct Vent
Model: ATI-540P-P
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 9.5 GPM at 40° F Rise, 7.5 GPM at 50° F Rise, 6.3 GPM at 60° F Rise, 5.4 GPM at 70° F Rise. 189k Effective BTU/h.
5.0 out of 55.0 out of 55.0 out of 55.0 out of 55.0 out of 5(6)
Ask a Question
$1,299.00
Only 5 In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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 Icon
2% Check Discount
Learn More About 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.
Add To Cart
Learn More About ATI-310-N
A.O. Smith
ATI-310 - 5.3 GPM at 60° F Rise - 0.80 UEF - Gas Tankless Water Heater - Power Vent
Model: ATI-310-N
4.8 out of 54.8 out of 54.8 out of 54.8 out of 54.8 out of 5(6)
Q&As (2)
$770.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATI-310C-N
A.O. Smith
ATI-310C - 5.3 GPM at 60° F Rise - 0.82 UEF - Gas Tankless Water Heater - Direct Vent
Model: ATI-310C-N
EnergyStar Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Concentric Vent. Ratings: 7.9 GPM at 40° F Rise, 6.2 GPM at 50° F Rise, 5.3 GPM at 60° F Rise, 4.5 GPM at 70° F Rise. 156k Effective BTU/h.
4.8 out of 54.8 out of 54.8 out of 54.8 out of 54.8 out of 5(6)
Ask a Question
$845.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATI-510C-N
A.O. Smith
ATI-510C - 5.5 GPM at 60° F Rise - 0.81 UEF - Gas Tankless Water Heater - Direct Vent
Model: ATI-510C-N
EnergyStar Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Concentric Vent. Ratings: 8.3 GPM at 40° F Rise, 6.9 GPM at 50° F Rise, 5.5 GPM at 60° F Rise, 4.8 GPM at 70° F Rise. 163k Effective BTU/h.
4.8 out of 54.8 out of 54.8 out of 54.8 out of 54.8 out of 5(6)
Ask a Question
$1,299.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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 Icon
2% Check Discount
Learn More About 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.
Add To Cart
Learn More About ATI-510-P
A.O. Smith
ATI-510 - 5.5 GPM at 60° F Rise - 0.80 UEF - Propane Tankless Water Heater - Power Vent
Model: ATI-510-P
EnergyStar Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 8.3 GPM at 40° F Rise, 6.9 GPM at 50° F Rise, 5.5 GPM at 60° F Rise, 4.8 GPM at 70° F Rise. 163k Effective BTU/h.
5.0 out of 55.0 out of 55.0 out of 55.0 out of 55.0 out of 5(4)
Ask a Question
$959.00
Factory-Direct
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATIO-910-N
A.O. Smith
ATIO-910 - 10.5 GPM at 60° F Rise - 80% Eff. - Gas Tankless Water Heater - Power Vent or Outdoor
Model: ATIO-910-N
Commercial Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 14.8 GPM at 40° F Rise, 12.5 GPM at 50° F Rise, 10.5 GPM at 60° F Rise, 8.5 GPM at 70° F Rise. 304k Effective BTU/h.
5.0 out of 55.0 out of 55.0 out of 55.0 out of 55.0 out of 5(1)
Ask a Question
$3,349.00
Only 1 In-Stock
Freight Icon
Free Shipping & Lift Gate
Learn More About Free Freight *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 Icon
2% Check Discount
Learn More About 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.
Add To Cart
Learn More About ATO-110-N
A.O. Smith
ATO-110 - 3.9 GPM at 60° F Rise - 0.79 UEF - Gas Tankless Water Heater - Outdoor
Model: ATO-110-N
EnergyStar Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 5.8 GPM at 40° F Rise, 4.5 GPM at 50° F Rise, 3.9 GPM at 60° F Rise, 3.3 GPM at 70° F Rise. 115k Effective BTU/h.
5.0 out of 55.0 out of 55.0 out of 55.0 out of 55.0 out of 5(1)
Ask a Question
$525.00
Only 1 In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATO-310-N
A.O. Smith
ATO-310 - 5.3 GPM at 60° F Rise - 0.80 UEF - Gas Tankless Water Heater - Outdoor
Model: ATO-310-N
EnergyStar Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 7.9 GPM at 40
Write a Review
Ask a Question
$799.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATO-510-N
A.O. Smith
ATO-510 - 5.5 GPM at 60° F Rise - 0.80 UEF - Gas Tankless Water Heater - Outdoor
Model: ATO-510-N
EnergyStar Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 8.3 GPM at 40° F Rise, 6.9 GPM at 50° F Rise, 5.5 GPM at 60° F Rise, 4.8 GPM at 70° F Rise. 163k Effective BTU/h.
Write a Review
Ask a Question
$959.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATO-540P-N
A.O. Smith
ATO-540P - 6.3 GPM at 60° F Rise - 0.95 UEF - Gas Tankless Water Heater - Outdoor
Model: ATO-540P-N
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 9.5 GPM at 40° F Rise, 7.5 GPM at 50° F Rise, 6.3 GPM at 60° F Rise, 5.4 GPM at 70° F Rise. 199k Effective BTU/h.
Write a Review
Ask a Question
$1,299.00
Only 5 In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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 Icon
2% Check Discount
Learn More About 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.
Add To Cart
Learn More About ATO-540P-P
A.O. Smith
ATO-540P - 6.3 GPM at 60° F Rise - 0.95 UEF - Propane Tankless Water Heater - Outdoor
Model: ATO-540P-P
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 9.5 GPM at 40° F Rise, 7.5 GPM at 50° F Rise, 6.3 GPM at 60° F Rise, 5.4 GPM at 70° F Rise. 199k Effective BTU/h.
Write a Review
Ask a Question
$1,299.00
In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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 Icon
2% Check Discount
Learn More About 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.
Add To Cart
Learn More About ATO-110U-N
A.O. Smith
ATO-110U - 3.9 GPM at 60° F Rise - 0.81 UEF - Gas Tankless Water Heater - Outdoor
Model: ATO-110U-N
EnergyStar Water Heater. Ultra Low NOx Emissions (SCAQMD Rule 1146.2 Compliant). Ratings: 5.8 GPM at 40
Write a Review
Ask a Question
$649.00
Factory-Direct
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATO-140H-N
A.O. Smith
ATO-140H - 3.8 GPM at 60° F Rise - 0.91 UEF - Gas Tankless Water Heater - Outdoor
Model: ATO-140H-N
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 5.4 GPM at 40° F Rise, 4.4 GPM at 50° F Rise, 3.8 GPM at 60° F Rise, 3.2 GPM at 70° F Rise. 112k Effective BTU/h.
Write a Review
Ask a Question
$735.00
Only 4 In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATO-240H-N
A.O. Smith
ATO-240H - 5.0 GPM at 60° F Rise - 0.95 UEF - Gas Tankless Water Heater - Outdoor
Model: ATO-240H-N
EnergyStar Condensing Water Heater. Low NOx Emissions (< 40 ng/J or 55 PPM). Ratings: 6.7 GPM at 40° F Rise, 6.1 GPM at 50° F Rise, 5.0 GPM at 60° F Rise, 4.3 GPM at 70° F Rise. 171k Effective BTU/h.
Write a Review
Ask a Question
$910.00
Only 3 In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart
Learn More About ATO-340H-N
A.O. Smith
ATO-340H - 5.7 GPM at 60° F Rise - 0.94 UEF - Gas Tankless Water Heater - Outdoor
Model: ATO-340H-N
Write a Review
Ask a Question
$999.00
Only 4 In-Stock
Freight Icon
Free Shipping
Learn More About Free Freight *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.
Add To Cart

ABOUT US
+−
COMMUNITY
+−
CUSTOMER SERVICE
+−
DISCOUNT DEN
+−
PARTNERSHIPS
+−
PRODUCT SUPPORT
+−
Experts
Better Business Bureau Internet Retailer Inc 5000
CALL TO ORDER
(866) 554-4328
Hide
Visit eComfort on Facebook
View the eComfort Twitter Profile Page
Follow eComfort on Pinterest
View eComfort YouTube Channel