DoesTheMath

Lennox WHHP065T45MD240S**** vs NAVIEN NWP500S065AUMB: which uses less energy?

At the high draw pattern the Lennox WHHP065T45MD240S**** uses 1,225 kWh a year and the NAVIEN NWP500S065AUMB 1,231 — 6 kWh (0%) less, about 61 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
Lennox WHHP065T45MD240S**** NAVIEN NWP500S065AUMB
UEF (Uniform Energy Factor) 4.05 (better) 4.03
Energy use per year (kWh) 1,225 (better) 1,231
First hour rating (gal) 77 80
Rated storage volume (gal) 61 61
Installed cost range $3,577–$4,851 $3,575–$4,831
ENERGY STAR certified yes yes
Refrigerant R-513A, GWP 630 R-134a, GWP 1430
On the market since 2025-12-01 2025-04-30
DOE CCD · 2026-09-19

What it costs to run

Lennox WHHP065T45MD240S****: 1,225 kWh a year NAVIEN NWP500S065AUMB: 1,231 kWh a year

Lennox WHHP065T45MD240S**** — 1,225 kWh a year NAVIEN NWP500S065AUMB — 1,231 kWh a year

Lennox WHHP065T45MD240S**** is 6 kWh a year lower than NAVIEN NWP500S065AUMB.

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.
  • Both are ENERGY STAR certified, which requires a manufacturer warranty of at least six years; the actual term for each model is not published.
  • Time on the market, as filed with ENERGY STAR: the Lennox WHHP065T45MD240S**** since 2025-12-01, the NAVIEN NWP500S065AUMB since 2025-04-30. A sale date, not a lifespan.

Which should you pick?

  • Pick the Lennox WHHP065T45MD240S**** if running cost matters most: it uses 6 kWh less a year on the same test.
  • Pick the NAVIEN NWP500S065AUMB if you need more hot water in your busiest hour: it lists a first hour rating of 80 gallons against 77.
  • Neither if your household's busiest hour needs more than 80 gallons of hot water — neither lists more. Check whether a 65-gallon heater is enough.

Each model on its own

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