Search  for anything...

A.O. Smith ENS-40 ProMax Short Electric Water Heater, 40 gal

  • Based on 10 reviews
Condition: New
Checking for product changes

Notify me when this product is back in stock

$1,043.08 Why this price?

Buy Now, Pay Later

As low as $58 / mo
  • – 18-month term
  • – No impact to credit
  • – Instant approval decision
  • – More plans available at checkout
Free shipping on this product

Availability: Unavailable
Fulfilled by ResearchWaterFilters
Available payment plans shown during checkout


  • Permaglas glass coating protects steel tank from corrosion and maximizes tank life
  • Dynaclean diffuser dip tube helps reduce lime and sediment buildup while maximizing hot water output; made from long-lasting PEX cross-linked polymer
  • CoreGard anode rode aluminum anode with stainless steel core protects tank against corrosion longer than ordinary steel anodes
  • Durable, tamper-resistant brass drain valve
  • Meets all current regulations set forth by the National Appliance Energy Conservation Act (NAECA)


The ProMax family of electric water heaters offers unmatched value and quality. The full product line meets the energy efficiency requirements set forth by the Department of Energy and qualifies for most utility rebate programs. All models are equipped with Permaglas glass coating, certified T&P relief valve, and long-lasting low-watt density copper heating elements. The Dynaclean dip tube reduces lime and sediment buildup for years of dependable hot water. And ProMax gives you plenty of installation choices - including tall, short and lowboy models.

Brand: ‎A. O. Smith

Capacity: ‎40 Gallons

Power Source: ‎Battery Powered

Item Dimensions LxWxH: ‎22 x 22 x 50 inches

Color: ‎Gray

Wattage: ‎4500 watts

Voltage: ‎240 Volts

Material: ‎Aluminum, Stainless Steel, Brass

Style: ‎Indoor Installation

Manufacturer: ‎Trumbull Industries

Part Number: ‎6 40 EORS

Item Weight: ‎124 pounds

Product Dimensions: ‎22 x 22 x 50 inches

Item model number: ‎ENS-40

Size: ‎40 gal

Item Package Quantity: ‎1

Batteries Required?: ‎No

Warranty Description: ‎6-year limited tank and parts warranty

Date First Available: May 15, 2015

Frequently asked questions

This product is currently out of stock. Please check back later for shipping info.

Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.

To initiate a return, please visit our Returns Center.

View our full returns policy here.

  • Klarna Financing
  • Klarna Pay in 4
  • ViaBill Easy Monthly Payments
Leasing options through Acima may also be available during checkout.

Learn more about financing & leasing here.

Top Amazon Reviews

  • Short Almost Caught The Unit On Fire
We have had an absolutely awful experience with A.O. Smith. I bought a 50 Gallon Electric Series 100 water heater from Lowe's in Tacoma, WA. This was bought on Feb 4th, 2023. We got a small amount of water that was warm, but after that first shower, none returned. We called AO Smith, and they said that they do not have agreements with anyone in the area to service, so they would reimburse $150 (plumbers/electricians won't even show up for that). I called and asked for a supervisor; one called me back but left no phone number or name. So, I called back, on Friday, Feb 10th, and was promised someone would call me back by the end of the day. No one did. I called Saturday, Feb 11th, and was promised I was next in line for a supervisor. No one called me back. But, I did email them photos of where the unit was poorly manufactured. The wire connecting the upper and lower thermostat had exposed wire and burned out the thermostat unit. Was told by authorities that this fault could have electrocuted someone (if it was mid-cycle) and potentially burned the house down. I called twice on Sunday, Feb 12th. I finally talked to a supervisor named Keith who was incredibly rude and told me he would reimburse the $150 if I took the water heater back out and took it to Lowes. Even with this information, I was not able to get a call from a supervisor. I emailed the CEO on Sunday, Feb 12th, and have yet to get a response (doubt I will). Because the 6-year warranty has not expired, Lowe's will not honor the extended warranty that I paid for. I wondered if I was an abnormal case, but, seems like based on the reviews that I am seeing, this company is doing an awful job when it comes to customer service. ... show more
Reviewed in the United States on February 13, 2023 by Heath Hollensbe Heath Hollensbe

  • Terrible
I would give this 0 stars if that were an option. I should have purchased a Rheem first (eventually what I did purchase) but I had no idea at the time that AOSmith was such a sleazy company. AOSmith has clearly adopted a "Cable Guy" business model. Sell cheaply made, substandard quality, fragile or defective products and then cite a 'warranty' that gives two options: (1) fix at your own expense ($200 minimum charge); or (2) forces an upgrade to a more expensive product. Good luck getting either of these, as their service numbers will keep you waiting on hold for hours, if anyone responds at all. Service personnel are rude and uninformed, but convey a consistent message: you bought it, you're stuck with it; you didn't read the 'fine print' on the warranty. We immediately on installation had issues with getting nothing but lukewarm (then cold) water from their tank and called their service number, gave model and serial numbers. It took three tries an a total of about 3.5 hours (they hang up after a certain number of minutes). The person on the other end tried to get me to check the top element (that DOES NOT EXIST... our water heater had only one element). After correcting them about the heater, they revised their statement about 2 elements and told us that one of their technicians (which I had to pay for at $100/hr) would need to verify that the water was not heating. Unfortunately, even at the max setting, the water does not get hot. One barely warm shower and have to wait at least an hour before water gets warm enough for another person. And, that's if nobody has washed dishes in the last 30 minutes. Worst water heater I've ever bought. Lowes is at fault as well. They now (in Phoenix) only sell AOSmith water heaters, and they will not warrant them, nor do they advise their customers on the lack of warranty support at AOSmith's end. They will not accept defective units unless you can convince AOSmith's phone people to provide an RA, which they are trained not to do. It's a pretty sleazy arrangement. Although I have been happy with Lowes' service in the past, this is probably the last time I will even walk into their stores. I'll be shopping at Home Depot in the future, and my replacement will be Rheem which does stand behind their products. ... show more
Reviewed in the United States on March 3, 2022 by James C. Westland

Can't find a product?

Find it on Amazon first, then paste the link below.