RELIANCE WATER HEATERS GUF-40 1** vs Ruud PROG40S-36N RH67 PV: which uses less energy?

At the medium draw pattern the RELIANCE WATER HEATERS GUF-40 1** and the Ruud PROG40S-36N RH67 PV use the same energy, 171 therms a year each, on the same federal test. Both are filed as a gas tank, so the comparison holds; what separates them is below. Enter your ZIP to price either one on your own rate.

Side by side

Compared within one class only: models filed as a gas tank at the medium draw pattern.

Filed and computed figures
Figure	RELIANCE WATER HEATERS GUF-40 1**	Ruud PROG40S-36N RH67 PV
UEF (Uniform Energy Factor)	0.65	0.65
Energy use per year (therms)	171	171
First hour rating (gal)	68	66
Rated storage volume (gal)	38	39
Installed cost range	$1,702–$2,914	$1,716–$2,950
ENERGY STAR certified	not matched	not matched

DOE CCD · 2026-09-19

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 below.
The actual warranty term is printed in each model’s documentation, not in any registry.

Which should you pick?

Pick the RELIANCE WATER HEATERS GUF-40 1** if its price or availability suits you — on energy the two are level.
Pick the Ruud PROG40S-36N RH67 PV if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the RELIANCE WATER HEATERS GUF-40 1**.
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

RELIANCE WATER HEATERS GUF-40 1**

Its filed figures, class position and running cost on your ZIP.
Ruud PROG40S-36N RH67 PV

Its filed figures, class position and running cost on your ZIP.