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Heat Pump Water HeatersHigh-efficiency electric replacements and hybrid tanks.Condensing Tankless Water HeatersCondensing whole-home flow with venting constraints.Gas Tank Water HeatersStraight swaps when gas storage is still the fit.

Plan Your Swap

Sizing guideCapacity, first-hour rating, and temperature-rise fit.Accessories hubInstall extras, code-adjacent parts, and paid-link accessory picks.Upgrade from NHP50Replacement candidates and projected operating-cost delta.Upgrade from NHP65Replacement candidates and projected operating-cost delta.Upgrade from NHP80Replacement candidates and projected operating-cost delta.Upgrade from NPE 210S2Replacement candidates and projected operating-cost delta.Upgrade from PROE50 T2 RH95Replacement candidates and projected operating-cost delta.HPTA 50 2 vs HPTA 80 2Side-by-side specs, efficiency, and fit differences.HPTS 50 2 vs NHP50Side-by-side specs, efficiency, and fit differences.NHP120 vs PROPH80 T2 RH400 30Side-by-side specs, efficiency, and fit differences.NPE 210S2 vs NPE 240S2Side-by-side specs, efficiency, and fit differences.

Guides & Data

California heat pump guideLocal rates, rebates, and operating costs.Colorado heat pump guideLocal rates, rebates, and operating costs.Massachusetts heat pump guideLocal rates, rebates, and operating costs.Oregon heat pump guideLocal rates, rebates, and operating costs.Washington heat pump guideLocal rates, rebates, and operating costs.DOE 2029 standardsWhat changes in 2029 and which product classes move first.

Brands

A.O. Smith Water HeatersPublished models, product lines, and brand coverage.Bradford White Water HeatersPublished models, product lines, and brand coverage.Navien Water HeatersPublished models, product lines, and brand coverage.Noritz Water HeatersPublished models, product lines, and brand coverage.Rheem Water HeatersPublished models, product lines, and brand coverage.Rinnai Water HeatersPublished models, product lines, and brand coverage.Takagi Water HeatersPublished models, product lines, and brand coverage.
Model specs

XG40T09HE40U0

Rheem / 38-Gallon Gas Tank Water Heater
Usually the simplest same-fuel swap, with lower efficiency than a heat pump.
ShortlistRunning costInstall changeFull specs
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, Dec 2025).
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" tall
What 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

Common install considerations for gas tank units

What is required depends on your existing installation, local code, and installer preference.

Thermal Expansion Tank Often required by code Check on Amazon (paid link)
Water Heater Drain Pan Often required by code Check on Amazon (paid link)
Earthquake Straps (Seismic Restraints) Often required by code Check on Amazon (paid link)
Full accessories list

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
UEF0.65
First Hour Rating81 gal
BTU Input40,000 BTU/hr
Est. Annual Energy263 therms/yr
Capacity
Storage Volume38 gal
Physical
Height63.75 in
Width19.5 in
Connections3/4 inch NPT
Venting
TypeNatural Draft
MaterialCategory I B Vent
Warranty
Tank9 yr
Parts9 yr
Labor2 yr
Keep the route moving

Other Rheem models and the full gas tank guide, if this one isn't the right fit.

Head-to-head comparisons
Gas Tank guideAll Rheem modelsUpgrade paths for this modelSizing guideInstallation accessoriesAll models
Sources. Home Depot, Manufacturer, Retailer listing, Rheem. Data compiled March 2026.Methodology
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