DoesTheMath

LG APHWC501M vs Reservoir N51: which uses less energy?

At the high draw pattern the LG APHWC501M uses 1,262 kWh a year and the Reservoir N51 1,405 — 143 kWh (10%) less, about 1,430 kWh over ten years. Both are filed as an electric tank, so the comparison holds. Enter your ZIP below to price the difference.


Side by side

Compared within one class only: models filed as an electric tank at the high draw pattern.

Filed and computed figures
Figure LG APHWC501M Reservoir N51
UEF (Uniform Energy Factor) 3.93 (better) 3.53
Energy use per year (kWh) 1,262 (better) 1,405
First hour rating (gal) 76 75
Rated storage volume (gal) 53 47
Installed cost range $3,304–$4,656 $3,064–$4,199
ENERGY STAR certified yes not matched
Refrigerant R-134a, GWP 1430 not filed
On the market since 2024-03-01 not filed
DOE CCD · 2026-09-19

What it costs to run

LG APHWC501M: 1,262 kWh a year Reservoir N51: 1,405 kWh a year

LG APHWC501M — 1,262 kWh a year Reservoir N51 — 1,405 kWh a year

LG APHWC501M is 143 kWh a year lower than Reservoir N51.

DOE CCD · 2026-09-19

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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 LG APHWC501M if running cost matters most: it uses 143 kWh less a year on the same test.
  • Pick the Reservoir N51 if the installed price matters more than the running cost: its modeled installed range is $3,064–$4,199 against $3,304–$4,656.
  • Neither if your household's busiest hour needs more than 76 gallons of hot water — neither lists more. Check whether a 50-gallon heater is enough.

Each model on its own