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A. O. Smith FMHR-40 4**

A. O. Smith FMHR-40 4** is in the DOE listing as of Oct 26, 2026.

It has a labeled size of 40 gallons, a certified storage volume of 38 gallons, a certified UEF of 0.58, and a certified first-hour rating of 59 gallons of hot water.

Its advertised UEF of 0.58 from A. O. Smith matches the certified 0.58 (Read Oct 4, 2026).

  • Gas storage water heater
  • 2 listed models

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

Storage volume
38gallons
UEF
0.58Uniform energy factor
First-hour rating
59gallonsHot water in the first hour
See it among every gas storage model

Advertised and certified figures

A. O. Smith FMHR-40 4**: advertised and certified
A. O. Smith FMHR-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 0.58, certified 0.58. First-hour rating: advertised 59 gal, certified 59 gal. 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 0.58 Certified 0.58 First-hour rating Advertised 59 gal Certified 59 gal
FigureAdvertisedCertifiedAdvertiserRead
Size 40 gal, nominal size 38 gal storage volume A. O. Smith Read Oct 4, 2026
Size 38 gal 38 gal storage volume A. O. Smith Read Oct 4, 2026
UEF 0.58 0.58 A. O. Smith Read Oct 4, 2026
First-hour rating 59 gal 59 gal A. O. Smith Read Oct 4, 2026

Certified figures by listed model

Model numberStorage volume (gal)UEFFirst-hour rating (gal)Recovery efficiencyDraw pattern
FMHR-40 4**380.585978%Medium
G6-MH4035NVR 4**380.585978%Medium

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 59 gallons in the test (its first-hour rating). Reheating lets it give 21 gallons beyond the 38 gallons in its tank. Among 763 gas storage models, 705 have a higher first-hour rating. Among gas storage models, the median first-hour rating is 78 gallons.

As of Oct 26, 2026, it was not listed as ENERGY STAR certified. In tests, 58% of the energy it uses ends up as hot water (UEF 0.58). The daily hot water use in the test, called its draw pattern, was medium. Among 288 gas storage models on its draw pattern, 230 have a higher UEF. A UEF of 0.60 is the median for its type and draw pattern. When it reheats water in the test, 78% of the energy it uses ends up in the water.

It is sold as FMHR-40 4** and G6-MH4035NVR 4**. There are 4 more basic models with the same test figures. Each of them is listed under a different brand.

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.