A.O. Smith EES-40 Water Heater Review: Is It Worth It?

A.O. Smith 40-Gallon Tall Electric Water Heater (EES-40)

Score: 8.4/10 — A dependable, practical electric tank water heater for small to medium households that want steady hot water, familiar maintenance, and solid long-term value without smart features or gas installation complexity.

Check Price on Amazon

Overview

The A.O. Smith 40-Gallon Tall Electric Water Heater is a traditional electric storage-tank water heater designed for everyday residential use in small to medium households.

If you are upgrading your entire plumbing system, you might also consider a high-quality kitchen faucet or a modern bath faucet to complement your new installation.

To protect this investment from sediment, many homeowners pair it with a GE GXWH40L whole house water filter system or a Culligan whole-house filtration system. With a 40-gallon capacity, dual electric heating elements, and a glass-lined tank, it targets homeowners who need reliable hot water for showers, dishwashing, laundry, and general household demand without the steep learning curve or high cost of hybrid systems.

This model is best suited to small and medium households, especially homes with one to three occupants or moderate hot-water usage. Its tall profile makes it a natural fit for garages, basements, utility rooms, or dedicated water heater closets where vertical clearance is available. Because it is electric, it avoids the venting requirements of gas water heaters, though it still requires the correct electrical connection and professional installation in most homes to ensure safety and compliance with local building codes.

The main appeal of the A.O. Smith 40-Gallon Tall Electric Water Heater (EES-40) is straightforward dependability. It does not try to be a high-end hybrid heat pump water heater or a connected smart appliance. Instead, it focuses on the essentials: a durable tank, consistent heating, adjustable temperature controls, and corrosion protection for long-term service. In an era of "smart" everything, there is significant value in a mechanical system that performs its primary function with unwavering consistency.

Key Features

Pros & Cons

Performance

In everyday use, the A.O. Smith 40-Gallon Tall Electric Water Heater provides a predictable and consistent experience. For a household of two or three people, the 40-gallon capacity is generally sufficient for the standard "morning rush." One person can take a full shower, and there will still be plenty of hot water for a second person to wash their hands or for a dishwasher to start its first cycle.

The dual heating elements prove their worth during recovery. Recovery time—the time it takes for the tank to return to its set temperature after being depleted—is generally slower in electric tanks than in gas tanks. However, the EES-40's dual-element design helps optimize this process. While you won't get the instantaneous recovery of a high-end commercial unit, it manages residential loads with ease, provided you aren't running three showers and a washing machine simultaneously.

The temperature stability is another high point. Once the thermostats are set, the EES-40 maintains a very tight tolerance. You won't experience the sudden temperature swings often associated with cheaper, single-element models. The water delivery is smooth, and the internal baffles help manage the flow to keep the output temperature consistent from the first gallon to the last.

How It Works: The Mechanics of the EES-40

To understand why the A.O. Smith 40-Gallon Tall Electric Water Heater (EES-40) is a staple in residential plumbing, it is helpful to look at the engineering inside the tank. This is a "storage" style heater, meaning it keeps a large volume of water hot and ready for immediate use. Unlike tankless heaters that heat water on demand, the EES-40 maintains a thermal reservoir.

The heating process is handled by dual electric elements. Typically, one element is located at the top and one at the bottom. This configuration is critical because hot water naturally rises (convection). The bottom element handles the bulk of the initial heating, while the top element ensures that the water being delivered to your taps stays at the desired temperature even as cold water enters the bottom of the tank. This minimizes the "cold water sandwich" effect where a layer of lukewarm water sits between the hot and cold layers.

Thermal expansion is another key factor. As water heats up, it expands. The EES-40 tank is engineered to handle this pressure, and when paired with a thermal expansion tank (see our Watts LFA-3/4 review for more on pressure regulation), it prevents the tank from stressing under pressure. The glass lining serves as a chemical barrier; without it, the oxygen and minerals in the water would cause the steel tank to rust from the inside out in a matter of years.

The "sacrificial" anode rod is the final piece of the durability puzzle. This rod is made of a more active metal (like magnesium or aluminum) than the steel of the tank. Through a process called electrolysis, the corrosive elements in the water attack the rod instead of the tank walls. As long as the rod is intact, the tank remains protected. This is why regular maintenance—specifically checking and replacing the anode rod—is the single most important factor in the lifespan of an A.O. Smith water heater.

Installation and Setup Guide

Installing the A.O. Smith 40-Gallon Tall Electric Water Heater (EES-40) requires a combination of plumbing and electrical expertise. Because it is a high-voltage appliance, professional installation is strongly recommended to ensure the unit is grounded and the circuit can handle the amperage load. For those coordinating multiple home upgrades, you might also check our guide to battery backup sump pumps to ensure your basement remains dry (see our Ridgid SP-650C review for a high-performance pump option).

Site Preparation and Positioning

The "Tall" aspect of the EES-40 means you must measure your vertical clearance carefully. Ensure there is enough room not only for the tank itself but also for the piping connections at the top and the electrical conduit. The unit should be placed on a level, non-combustible surface. Many homeowners prefer placing the unit on a plastic water heater pan; this protects the flooring in the event of a future leak or tank failure. If your water heater is located in a basement prone to moisture, we recommend using a high-capacity dehumidifier and pairing your setup with a Wayne ESP25 battery backup sump pump, or exploring our guide to the best submersible utility pumps (or check our Ridgid SP-650C review for a specific recommendation for added peace of mind.

Plumbing Connections

The unit features standard inlets and outlets. For those performing the installation, using a high-quality SharkBite coupling can simplify the process (see our detailed coupling guide for fitment tips). It is highly recommended to use flexible connectors rather than rigid copper piping. Flexible connectors reduce the risk of stress fractures in the pipes caused by the slight shifting of the tank during heating cycles. A shut-off valve must be installed on the cold water inlet to allow for easy maintenance or emergency shut-down.

Electrical Wiring

The EES-40 requires a dedicated 240V circuit (and appropriate circuit protection). The wiring must be run through an approved junction box and connected to the heater's internal wiring. If you are updating your panel, see our review of AFCI breakers for modern safety standards. Ensuring that the ground wire is securely attached is critical for safety. Overloading the circuit or using an improper wire gauge can lead to tripped breakers or, in worst-case scenarios, electrical fires.

To prime correctly: Open a hot water tap somewhere in the house, slowly open the cold water supply valve to the heater, and wait until water flows steadily from the open tap without air bubbles. Only then should you flip the breaker to provide power to the unit.

Long-Term Maintenance and Care

A water heater is not a "set it and forget it" appliance. To get the full expected lifespan out of the A.O. Smith 40-Gallon Tall Electric Water Heater (EES-40), a basic maintenance schedule is required.

Flushing the Tank

Over time, sediment (mostly calcium and magnesium) settles at the bottom of the tank. This sediment creates a layer of insulation between the bottom heating element and the water, forcing the element to work harder and potentially burn out. It can also cause "rumbling" noises during heating. We recommend flushing the tank once a year. To reduce sediment buildup in the first place, consider installing a whole house water filter like the GE GXWH40L system (check our guide on whole-house filtration for more options) to mitigate mineral accumulation. This involves attaching a garden hose to the drain valve at the bottom and running the water until it runs clear.

Anode Rod Inspection

Depending on the mineral content of your local water (hard water vs. soft water), the rod may deplete every 2 to 5 years. If the rod is completely dissolved, the water will begin attacking the steel tank. Periodically unscrewing the anode rod to check its condition can add years to the life of the EES-40.

Thermostat Calibration

Check your temperature settings annually. The ideal setting is typically around 120°F (49°C). This is hot enough to kill most bacteria and provide a comfortable shower, but cool enough to prevent scalding and reduce the risk of lime scale buildup in the tank.

Buyer's Guide: Is the EES-40 Right for You?

Choosing the right water heater depends on three main factors: household size, available space, and budget. The A.O. Smith 40-Gallon Tall Electric Water Heater (EES-40) sits in the "sweet spot" for a large portion of the residential market, but it isn't for everyone.

Analyzing Capacity (40 Gallons)

Capacity is often the most misunderstood part of the buying process. Many people assume a "gallon" of storage is a gallon of usable hot water. In reality, you have a "first hour rating" which tells you how much hot water the unit can actually deliver in 60 minutes, accounting for the cold water that enters the tank as hot water exits. For a 40-gallon tank like the EES-40, this is generally sufficient for:

• 1-2 persons: Overkill, plenty of water.
• 3 persons: Ideal, assuming standard usage.
• 4+ persons: Potentially problematic if multiple people shower back-to-back.

If you have a large soaking tub or a rain-shower head with a high flow rate, you may find the 40-gallon capacity limiting. However, for standard showerheads and faucets, it provides a comfortable buffer.

The Trade-off: Tall vs. Short Profile

The EES-40 is the "Tall" version of the 40-gallon line. This is a critical distinction. A tall heater takes up less floor space (smaller diameter) but requires more vertical headroom. If you are installing this in a crawlspace or a basement with low-hanging ductwork, you must verify your measurements. If you lack vertical space, you would need to look for a "short" or "low-boy" model, or

For very specific low-demand areas, we recommend the