Model specs
XG40T09HE40U0
Rheem / 38-Gallon Gas Tank Water Heater
Usually the simplest same-fuel swap, with lower efficiency than a heat pump.
UEF0.65Certified efficiency
First hour81 galHot water delivery
Height63.75"Primary fit constraint
Running cost~$358/yrU.S. average natural gas
What this unit costs to run each year, and what switching to a heat pump would save.
XG40T09HE40U0 operating cost
Estimated annual operating cost: $358
Switching to a heat pump water heater could cut that to roughly $125/yr, saving ~$233/yr.
U.S. avg natural gas: $1.36/therm (EIA, Jan 2026).
Your state changes the cost. Ranges from $174/yr to $1312/yr depending on your state's natural gas rate.
XG40T09HE40U0 cost by state
Ranges from $174/yr to $1312/yr depending on your state's natural gas rate. U.S. average: $358/yr.
Alabama$431/yr$1.64/therm
Alaska$323/yr$1.23/therm
Arizona$455/yr$1.73/therm
Arkansas$500/yr$1.90/therm
California$602/yr$2.29/therm
Colorado$263/yr$1.00/therm
Connecticut$410/yr$1.56/therm
Delaware$434/yr$1.65/therm
District of Columbia$387/yr$1.47/therm
Florida$600/yr$2.28/therm
Georgia$421/yr$1.60/therm
Hawaii$1312/yr$4.99/therm
Idaho$174/yr$0.66/therm
Illinois$239/yr$0.91/therm
Indiana$260/yr$0.99/therm
Iowa$224/yr$0.85/therm
Kansas$318/yr$1.21/therm
Kentucky$318/yr$1.21/therm
Louisiana$421/yr$1.60/therm
Maryland$402/yr$1.53/therm
Massachusetts$652/yr$2.48/therm
Michigan$260/yr$0.99/therm
Minnesota$239/yr$0.91/therm
Mississippi$368/yr$1.40/therm
Missouri$371/yr$1.41/therm
Montana$224/yr$0.85/therm
Nebraska$260/yr$0.99/therm
Nevada$252/yr$0.96/therm
New Hampshire$487/yr$1.85/therm
New Jersey$366/yr$1.39/therm
New Mexico$281/yr$1.07/therm
New York$408/yr$1.55/therm
North Carolina$452/yr$1.72/therm
North Dakota$216/yr$0.82/therm
Ohio$284/yr$1.08/therm
Oklahoma$281/yr$1.07/therm
Oregon$447/yr$1.70/therm
Pennsylvania$352/yr$1.34/therm
Rhode Island$618/yr$2.35/therm
South Carolina$416/yr$1.58/therm
South Dakota$224/yr$0.85/therm
Tennessee$287/yr$1.09/therm
Texas$489/yr$1.86/therm
Utah$274/yr$1.04/therm
Vermont$423/yr$1.61/therm
Virginia$392/yr$1.49/therm
Washington$394/yr$1.50/therm
West Virginia$316/yr$1.20/therm
Wisconsin$279/yr$1.06/therm
Wyoming$276/yr$1.05/therm
Based on 263 therm/yr (ENERGY STAR rated) at each state's residential natural gas rate (EIA, Jan 2026).
How the XG40T09HE40U0 compares to other gas tank models.
Where this model fits
XG40T09HE40U0: 38-gallon · UEF 0.65 · 63.75″ tall. Only Rheem gas tank in the 40-gallon class right now.
Compare to other gas tank models:
Rheem XG50T09HE40U048 gal vs 38 gal · UEF 0.64 vs 0.65 · 62.75" vs 63.75" tallWithin Rheem's 40-gallon gas tank lineup, this page fills a specific role.
Where it sits in the Rheem lineup
- This is the efficiency leader in Rheem's 40-gallon gas tank lineup at 0.65 UEF, ahead of Rheem XG50T09HE40U0 at 0.64.
- Hot-water delivery is at the top of this brand bucket at 81 first-hour gallons.
Closest same-brand alternatives:
Rheem XG50T09HE40U0What changes if you upgrade or replace this unit.
Upgrading from the XG40T09HE40U0
Upgrade to a heat pump
New 240V/30A circuit required. Your gas tank runs without heavy electrical. A heat pump needs a dedicated 240V circuit.
Gas line capped. No more gas bill for hot water.
Condensate drain needed. Floor drain or condensate pump required.
Taller unit. Heat pumps are typically 60-75" tall. Measure overhead clearance.
Existing flue and B-vent can be removed.
Two trades needed (plumber + electrician). Biggest operating cost reduction available.
Upgrade to gas tankless
Uses existing gas line, but may need upsized supply for higher BTU input.
New venting required. Tankless uses direct-vent or power-vent, not your existing B-vent flue.
Wall-mounted. Frees the floor space where this tank stands.
Different hot water delivery. Endless supply, but lower peak flow than a tank’s first-hour rating.
Stays on gas. Better efficiency, endless hot water, but venting rework is the main cost.
Replace with another gas tank
Same gas line. Same B-vent flue. Same water connections.
Standard 63.75" height. Fits most existing tank spaces.
No electrical changes. No condensate drain.
Fewest changes if replacing with the same type. Verify gas line sizing and venting compatibility.
Usually a straightforward swap, but check the dimensions. Height, width, and service connections need to match what's already there.
XG40T09HE40U0 installation specifications
Dimensions
Height63.75 in
Width19.5 in
Connections3/4 inch NPT
Venting
TypeNatural Draft
MaterialCategory I B Vent
CategoryI
Safety and installation warnings
These warnings apply to this water heater type. Always follow the manufacturer's installation instructions and local building codes. Hire a licensed professional for installation.
Carbon monoxide hazard. Gas water heaters produce combustion byproducts including carbon monoxide (CO). Proper venting is essential. Never operate a gas water heater with damaged, disconnected, or blocked venting. Install a CO detector near the unit. If you smell gas or suspect a CO leak, leave the building and call your gas utility.
Garage installation. Gas water heaters installed in garages must have the ignition source at least 18 inches above the floor (IRC G2408.2) to prevent ignition of gasoline vapors. An elevated platform or wall-mount is required.
Fuel type match. Natural gas and propane (LP) models use different orifice sizes. Using the wrong fuel type causes incomplete combustion and carbon monoxide production. Verify the unit matches your fuel supply before installation. Conversion kits are available for some models but must be installed by a qualified technician.
Combustion air supply. Gas water heaters require adequate combustion air per local code (IRC/IMC). A unit in a confined space (closet, utility room) without proper air supply can backdraft, producing carbon monoxide. Ensure the installation space meets combustion air requirements for the unit's BTU input.
T&P relief valve. Every tank-type water heater has a temperature and pressure relief (T&P) valve. This is a critical safety device that prevents tank rupture by releasing water if temperature exceeds 210°F or pressure exceeds 150 PSI. The discharge pipe must run to within 6 inches of the floor or to an exterior drain. Never cap or plug the T&P valve. Test it annually.
Scald prevention. The recommended maximum water temperature is 120°F to prevent scalding. Higher temperatures (130-140°F) reduce Legionella bacteria risk but require a thermostatic mixing valve at the outlet to deliver safe temperatures at fixtures. Some jurisdictions require mixing valves when the tank is set above 120°F.
Common install considerations for gas tank units
What is required depends on your existing installation, local code, and installer preference.
Warranty
Coverage
Tank9 yr
Parts9 yr
Labor2 yr
Common questions about the Rheem XG40T09HE40U0
From manufacturer specs, EIA energy data, and DOE regulations.
How much does the XG40T09HE40U0 cost to run per year?
~$358/yr at the U.S. average natural gas rate.
How much hot water does the XG40T09HE40U0 deliver?
81 gallons in the first hour from a 38-gallon tank. Suitable for a household of 1 to 3 people at medium draw.
Will the XG40T09HE40U0 fit in my space?
63.75" tall, 19.5" wide. Measure your space including clearances before ordering.
What warranty does the XG40T09HE40U0 come with?
9-year tank warranty, 9-year parts. Register with Rheem after installation to activate full coverage.
Full specifications
| Performance | |
| UEF | 0.65 |
|---|---|
| First Hour Rating | 81 gal |
| BTU Input | 40,000 BTU/hr |
| Est. Annual Energy | 263 therms/yr |
| Capacity | |
| Storage Volume | 38 gal |
| Physical | |
| Height | 63.75 in |
| Width | 19.5 in |
| Connections | 3/4 inch NPT |
| Venting | |
| Type | Natural Draft |
| Material | Category I B Vent |
| Warranty | |
| Tank | 9 yr |
| Parts | 9 yr |
| Labor | 2 yr |
Keep the route moving
Other Rheem models and the full gas tank guide, if this one isn't the right fit.
- PROE50 T2 RH95 47-gal electric tank
- PROPH40 T2 RH400-30 36-gal heat pump
- PROPH50 T2 RH400-30 45-gal heat pump
- PROPH65 T2 RH400-30 59-gal heat pump
- PROPH80 T2 RH400-30 72-gal heat pump
Sources. Home Depot, Manufacturer, Retailer listing, Rheem. Specs last verified 2026-03-26.Methodology
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