A. O. Smith GCBL-40 4** vs Ruud PROG39S-38U RH62 EC1*: which uses less energy?
An asterisk in a model number stands for any character: one filing covers several variants.
At the medium draw pattern the Ruud PROG39S-38U RH62 EC1* uses 188 therms a year and the A. O. Smith GCBL-40 4** 194 — 7 therms (3%) less, about 66 therms over ten years. Both are filed as a gas tank, so the comparison holds. Enter your ZIP below to price the difference.
Side by side
Compared within one class only: models filed as a gas tank at the medium draw pattern.
| Figure | A. O. Smith GCBL-40 4** | Ruud PROG39S-38U RH62 EC1* |
|---|---|---|
| UEF (Uniform Energy Factor) | 0.57 | 0.59 (better) |
| Energy use per year (therms) | 194 | 188 (better) |
| First hour rating (gal) | 68 | 68 |
| Rated storage volume (gal) | 38 | 37 |
| Installed cost range | not published | not published |
| CPSC recall naming it CPSC | none on file | none on file |
DOE CCD · 2026-09-19 CPSC · 2026-09-24
What it costs to run
Reliability
Not published: Reliability, failure rates and each model’s actual warranty term.
The registries these figures come from certify energy performance under a federal test; none of them records how long a unit lasts or how often it fails, so this page does not rank the two on reliability.
What is here instead:
- The filed efficiency, capacity and tank size of both models, side by side above.
- No CPSC recall on file names either model (list checked 2026-09-24).
- The actual warranty term is printed in each model’s documentation, not in any registry.
Which should you pick?
- Pick the Ruud PROG39S-38U RH62 EC1* if running cost matters most: it uses 7 therms less a year on the same test.
- Pick the A. O. Smith GCBL-40 4** if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the Ruud PROG39S-38U RH62 EC1*.
- Neither if your household's busiest hour needs more than 68 gallons of hot water — neither lists more. Check whether a 40-gallon heater is enough.
Each model on its own
- A. O. Smith GCBL-40 4** 194 therms a year
- Ruud PROG39S-38U RH62 EC1* 188 therms a year