Hot Water List
Menu

State GCB-40 4**

State GCB-40 4** is in the DOE listing as of Oct 26, 2026.

  • Gas storage water heater
  • 3 listed models

Not listed as ENERGY STAR certified on Oct 26, 2026.

Its figures are also listed under A. O. Smith GCB-40 4**.

Storage volume
38gallons
UEF
0.64Uniform energy factor
First-hour rating
78gallonsHot water in the first hour
See it among every gas storage model

Advertised and certified figures

State GCB-40 4**: advertised and certified
State GCB-40 4**: advertised and certified Size: advertised 40 gal, certified 38 gal (advertised nominal size, certified storage volume). Size: advertised 38 gal, certified 38 gal (certified storage volume). UEF: advertised 0.64, certified 0.64. UEF: advertised 0.64, certified 0.64 (advertised up to). Size · advertised nominal size, certified storage volume Advertised 40 gal Certified 38 gal Size · certified storage volume Advertised 38 gal Certified 38 gal UEF Advertised 0.64 Certified 0.64 UEF · advertised up to Advertised 0.64 Certified 0.64
FigureAdvertisedCertifiedAdvertiserRead
Size 40 gal, nominal size 38 gal storage volume State Read Oct 4, 2026
Size 38 gal 38 gal storage volume State Read Oct 4, 2026
UEF 0.64 0.64 State Read Oct 4, 2026
UEF up to 0.64 0.64 State Read Oct 4, 2026
First-hour rating 78 gal 78 gal State Read Oct 4, 2026

Certified figures by listed model

Model numberStorage volume (gal)UEFFirst-hour rating (gal)Recovery efficiencyDraw pattern
GS6-40-BRBT 4**380.647877%High
GS6-40-BRBT 4*1380.647877%High
GSX-40-BRBT380.647877%High

UEF is the uniform energy factor. A dash means the model has no such figure.

It holds 38 gallons in the test, 2 gallons less than its 40-gallon sold size. Over one hour from a full tank, it gave 78 gallons in the test (its first-hour rating). That is 40 gallons more than its tank holds, since it reheats during the hour. In the first hour, 366 of the 763 gas storage models give more hot water. In first-hour rating, it ties the median gas storage model.

It was not listed as ENERGY STAR certified on Oct 26, 2026. In tests, 64% of the energy went to hot water, so its UEF is 0.64. Its test ran at the high level of daily hot water use. Of 434 gas storage models with the same draw pattern, 255 have a higher UEF. For its type and draw pattern, the UEF runs from 0.61 to 0.90. When it reheats water in the test, 77% of the energy it uses ends up in the water.

It is the basic model for GS6-40-BRBT 4**, GS6-40-BRBT 4*1, and GSX-40-BRBT. Its test figures match those of 5 other basic models. Each of them is listed under a different brand. For the full group, see the A. O. Smith GCB-40 4** page.

Also listed as

They carry every figure in the table above.

Updated Oct 26, 2026 · Methodology

Not covered

  • Changes to an advertised figure after the date beside it.