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Best 40 Gallon Gas Hot Water Heater

3 expert-curated picks ranked by performance, value, and long-term reliability

40-gallon gas hot water heaters serve smaller households (1-3 people) and installs where the 50-gallon won't fit dimensionally. The 40-gallon capacity is the secondary residential gas tank size after 50-gallon, accounting for about 25% of US gas tank installs.

Top 40-gallon gas picks

Best overall: Rheem Performance Platinum 40-gal Gas

40,000 BTU, 70-gal FHR, UEF 0.64, 12-year warranty. About $749 unit, $1,500 installed.

Best plumber-installed: Bradford White RG240T6N 40-gal

40K BTU, 73-gal FHR, UEF 0.62, 6-year warranty. ICON gas control runs through power outages. About $1,950 plumber-installed.

Best budget: Rheem Fury 40-gal (82V40-2)

40K BTU, 6-year warranty, UEF 0.58. About $1,250 installed.

Best safety (garage installs): Bradford White Defender 40-gal

FVIR safety system targets garage installs where flammable vapors may be present. About $1,750 plumber-installed.

Best AO Smith / Lowe's: AO Smith Conservationist GCR-40

40K BTU, 70-gal FHR, UEF 0.62, 6-year warranty. About $1,350 installed.

When 40 is right vs when to upsize to 50

40-gallon is the right choice when:

  • 1-2 person household with sequential demand
  • Closet height restriction (40-gallon: 52" tall vs 50-gallon: 60" tall)
  • Mobile home / manufactured home (MH-specific 40-gallon units common)
  • Single-bathroom home regardless of household size

50-gallon is right instead when:

  • 3+ person household with overlapping or near-overlapping demand
  • Hot-water-intensive appliances (dishwasher, washing machine running hot wash)
  • Growing family (kids who'll become teenage shower-takers)

Install checks before ordering

  1. Measure closet height — 40-gallon needs ~58" interior height (52" tank + 6" venting overhead)
  2. Verify gas line is 1/2" or larger (sufficient for 40K BTU)
  3. Verify B-vent connection diameter matches new unit (most modern 40-gallon units use 3")
  4. 120V outlet within 6 feet for electronic ignition
  5. Drain pan + drain line if install is above living space
  6. Expansion tank requirement (check if main supply has check valve or PRV)

Install cost

  • Like-for-like 40-gallon atmospheric replacement: $1,250-$1,500
  • Atmospheric → power-vent conversion: $1,700-$2,300
  • Atmospheric → condensing conversion: $2,300-$2,900
  • Emergency same-day install: +$300-$700
3 products
$949 – $1,795
Updated May 2026

Quick Comparison

# Product Brand Rating Price
1 Rinnai RU199iN Sensei Tankless Water Heater Rinnai 4.8 Check current price Amazon
2 Rheem Performance Platinum 50-Gallon Gas Water Heater Rheem 4.6 Check current price Amazon
3 AO Smith Signature Premier 50-Gallon Gas Water Heater AO Smith 4.5 Check current price Amazon