A 40-gallon gas water heater can suit a smaller household or a home with moderate hot-water needs, but the right choice depends on more than tank size. Check whether your home uses natural gas or propane, confirm the heater’s venting and installation requirements, and compare the details available for each model. The options below include two natural-gas models and one liquid-propane model, so they are not interchangeable.
Quick Comparison
| Product | Fuel | Key details | Availability in supplied data |
|---|---|---|---|
| Rheem Professional Classic Tall Atmospheric 40-Gallon Water Heater | Natural gas | 40 gallons; 38,000 Btuh; tall atmospheric design | Marked available |
| GE RealMAX Choice 40-Gallon Tall Water Heater | Natural gas | 40 gallons; tall atmospheric design | Marked unavailable |
| A. O. Smith GCR-40LP ProMax Plus Water Heater | Liquid propane | 40 gallons; electronic gas valve; corrosion-resistant tank lining | Marked unavailable |
Our Picks: Best Gas Hot Water Heater 40 Gallon reviews
Rheem Professional Classic: A Natural-Gas Pick with a Stated 38,000-Btuh Input
This Rheem is a 40-gallon natural-gas water heater with a tall atmospheric design and a listed input of 38,000 Btuh. Those details make it a relevant option if your home already has a compatible natural-gas connection and venting setup. The supplied product information describes it as a durable model, but does not provide further construction specifications.
A 40-gallon tank can be a practical size for households with moderate hot-water demand. Still, tank capacity alone does not tell you exactly how well a heater will keep up with your routine. Consider how many people use hot water at once and whether your existing installation can accommodate a tall atmospheric unit.
Compared with the GE, the Rheem listing includes a specific input rating, which gives you one more detail to discuss with an installer. Compared with the A. O. Smith, it uses natural gas rather than liquid propane. These fuel types should not be treated as interchangeable.
Pros:
- 40-gallon capacity for a range of moderate household needs
- Natural-gas model with a stated 38,000-Btuh input
- Tall atmospheric design is clearly identified in the product name
- Marked available in the supplied product data
Cons:
- The supplied description gives limited detail about controls and construction
- Its tall form and atmospheric venting must suit your installation space and vent setup
Verdict: Choose the Rheem if you need a 40-gallon natural-gas atmospheric model and its size, venting, and connection requirements match your home.
GE RealMAX Choice: A Tall 40-Gallon Natural-Gas Option
The GE RealMAX Choice is listed as a 40-gallon, tall, atmospheric natural-gas water heater. Its stated configuration may be a fit for a home already set up for a conventional atmospheric unit, provided the heater’s dimensions and installation requirements match the space.
The supplied product data does not include a burner input rating, efficiency figure, or further feature details. That makes it harder to compare this model closely with the Rheem, which has a listed Btuh input, or the A. O. Smith, which has several described components. Before buying, check the product listing and manufacturer information for the specifications needed by your installer.
The supplied data marks this model unavailable. If the listing becomes accessible, confirm availability and verify the exact model details before making a decision. Its stated fuel is natural gas, not liquid propane.
Pros:
- 40-gallon tank capacity
- Tall atmospheric configuration is identified in the product name
- Natural-gas fuel type is clearly stated
Cons:
- Marked unavailable in the supplied product data
- The supplied description does not provide input, efficiency, or feature specifications
Verdict: Consider the GE only if it is available and its complete specifications, dimensions, and venting requirements check out for your home.
A. O. Smith ProMax Plus: A Propane Model with Detailed Internal Features
The A. O. Smith GCR-40LP is a 40-gallon liquid-propane water heater. Its LP fuel designation is the key detail: it is intended for a propane setup, so it is not a direct substitute for a natural-gas heater. The product title calls it high efficiency, but the supplied information does not include a numerical efficiency rating.
The listed features include a Blue Diamond glass coating, which the product description says provides corrosion resistance, and a self-powered electronic gas valve. The valve uses a thermopile to generate power for the electronic gas control, so the description says it does not require external power. A microprocessor is also described as helping manage operating parameters and temperature sensing.
The Dynaclean diffuser dip tube is designed to help reduce lime and sediment buildup and support hot-water output. The description identifies it as a PEX cross-linked polymer component. The product information also states that the heater meets current NAECA regulations. These details offer more to assess than the sparse GE listing, but the supplied data marks the A. O. Smith unavailable.
Pros:
- 40-gallon capacity for a propane-equipped home
- Self-powered electronic gas valve, according to the product description
- Blue Diamond glass coating and a diffuser dip tube are among the stated features
- Product description states that it meets NAECA requirements
Cons:
- Uses liquid propane, not natural gas
- Marked unavailable in the supplied product data
Verdict: This A. O. Smith is the option to investigate if your home uses propane and you want the listed electronic controls and corrosion-resistance features, but confirm availability and installation compatibility first.
How to Choose a 40-Gallon Gas Water Heater
Match the Fuel to Your Home
Start by confirming whether your home uses natural gas or liquid propane. The Rheem and GE models listed here are natural-gas units, while the A. O. Smith is an LP model. Choose a heater designed for your fuel supply, and ask a qualified installer to verify the connection. Do not assume a natural-gas model can be used with propane, or the reverse.
Check the Venting Type
The Rheem and GE product names specify atmospheric designs. Your home must have a compatible venting arrangement, and the heater must be installed according to its manufacturer instructions and local requirements. Confirm the vent type before ordering; a tank that fits the room may still be unsuitable for its vent setup.
Measure the Installation Space
Both natural-gas models are described as tall. Measure the available height and width, and leave room for the connections and access required for installation and maintenance. Use the manufacturer’s dimensions rather than estimating from the product photo.
Consider Your Household’s Hot-Water Use
A 40-gallon tank may suit moderate demand, but the right capacity depends on your household’s routines. Think about how often showers, laundry, and dishwashing overlap. If hot-water use is concentrated at the same time, ask an installer whether a 40-gallon tank is appropriate for your home instead of relying on tank volume alone.
Compare the Specifications You Can Verify
Look for the details your installer needs, including fuel, input rating, dimensions, venting type, and any stated efficiency information. The Rheem listing provides a 38,000-Btuh input, while the GE information supplied here does not include an input rating. The A. O. Smith description names several internal features but does not provide a numerical efficiency figure.
Check Availability and Installation Requirements
Product availability can change, and two of these models are marked unavailable in the supplied data. Check the product page for current listing information, then confirm installation requirements with a qualified professional. The right choice needs to fit your fuel source, venting, space, and local installation rules.
Frequently Asked Questions
Is a 40-gallon gas water heater large enough for a family?
It depends on how many people use hot water and whether several fixtures run at once. Consider your household’s peak demand and ask an installer to assess whether a 40-gallon tank is a good match.
Can I use the A. O. Smith propane model with natural gas?
The supplied product information identifies the A. O. Smith GCR-40LP as a liquid-propane model. Do not assume it is compatible with natural gas. Confirm fuel requirements with the manufacturer or a qualified installer.
What does atmospheric venting mean for installation?
It identifies the heater’s venting configuration. Your existing vent must be compatible with the specific model and installed according to the manufacturer’s instructions and applicable local requirements.
Which model has a stated input rating?
The Rheem listing specifies a 38,000-Btuh input. The supplied GE and A. O. Smith product information does not state an input rating.
Does the A. O. Smith model need external power for its gas control?
Its supplied description says the self-powered electronic gas valve uses a thermopile to generate the power needed for the electronic gas control without external power. Confirm the full installation details with the manufacturer or installer.
What should I verify before ordering?
Confirm fuel type, venting compatibility, dimensions, input and efficiency details, and the installation requirements for your home. Also check the product page because availability may change.
Final Recommendation
For a natural-gas home, the Rheem is the clearest choice in this group because its listing identifies the fuel, tall atmospheric design, 40-gallon capacity, and 38,000-Btuh input. The GE shares the 40-gallon natural-gas atmospheric setup, but the supplied details are sparse and mark it unavailable. For a propane home, the A. O. Smith offers the most detailed list of internal features, but it is a different fuel type and is also marked unavailable. Confirm current availability and have an installer verify compatibility before choosing any model.