A. O. Smith GUF-40 1**
A. O. Smith GUF-40 1** 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 0.65, and a certified first-hour rating of 68 gallons of hot water.
Its advertised UEF of 0.65 from A. O. Smith matches the certified 0.65 (Read Oct 5, 2026).
- Gas storage water heater
- 2 listed models
Not listed as ENERGY STAR certified on Oct 26, 2026.
Certified figures
- Storage volume
- 38gallons
- UEF
- 0.65Uniform energy factor
- First-hour rating
- 68gallonsHot water in the first hour
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| Figure | Advertised | Certified | Advertiser | Read |
|---|---|---|---|---|
| Size | 40 gal, nominal size | 38 gal storage volume | A. O. Smith | Read Oct 5, 2026 |
| Size | 38 gal | 38 gal storage volume | A. O. Smith | Read Oct 5, 2026 |
| UEF | 0.65 | 0.65 | A. O. Smith | Read Oct 5, 2026 |
| UEF | up to 0.65 | 0.65 | A. O. Smith | Read Oct 5, 2026 |
| First-hour rating | 68 gal | 68 gal | A. O. Smith | Read Oct 5, 2026 |
Certified figures by listed model
| Model number | Storage volume (gal) | UEF | First-hour rating (gal) | Recovery efficiency | Draw pattern |
|---|---|---|---|---|---|
| G12-UFDT4040NV 1** | 38 | 0.65 | 68 | 73% | Medium |
| GUF-40 1** | 38 | 0.65 | 68 | 73% | 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. Starting full, it gives 68 gallons of hot water in its first hour of use. Its tank holds 38 gallons, so reheating adds 30 gallons during the first hour. Of 763 gas storage models, 529 give more hot water in the first hour. The median gas storage model gives 78 gallons in its first hour.
On Oct 26, 2026, this heater was not listed as ENERGY STAR certified. In tests, 65% of the energy went to hot water, so its UEF is 0.65. Its test ran at the medium level of daily hot water use. Its UEF is lower than that of 32 of the 288 gas storage models with its draw pattern. For its type and draw pattern, the UEF runs from 0.57 to 0.75. Of the energy spent to reheat water, 73% goes into it (its recovery efficiency).
Its 2 model numbers are G12-UFDT4040NV 1** and GUF-40 1**. Its test figures match those of 3 other basic models. The American, RELIANCE WATER HEATERS, and State brands list one or more of them.
In one state, one rebate program may accept it.
Also listed as
They carry every figure in the table above.
Rebates
| Program | State | Status | Program page |
|---|---|---|---|
| Xcel Energy MINNESOTA RESIDENTIAL ENERGY EFFICIENCY PROGRAMS (gas storage, gas tankless) | MN | May qualify | Its own page |
Programs change their terms. Check the program's own page before you buy.
- Every A. O. Smith basic model
- Every 40-gallon gas storage water heater
- Every gas storage water heater
- The most-searched gas storage models side by side
Not covered
- Changes to an advertised figure after the date beside it.