DoesTheMath

FRIEDRICH PRO H40 T2 RH310BM vs Lennox WHES040T45TD240S****: which uses less energy?

At the medium draw pattern the FRIEDRICH PRO H40 T2 RH310BM uses 928 kWh a year and the Lennox WHES040T45TD240S**** 3,531 — 2,603 kWh (74%) less, about 26,026 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 medium draw pattern.

Filed and computed figures
FRIEDRICH PRO H40 T2 RH310BM Lennox WHES040T45TD240S****
UEF (Uniform Energy Factor) 3.5 (better) 0.92
Energy use per year (kWh) 928 (better) 3,531
First hour rating (gal) 60 58
Rated storage volume (gal) 36 36
Installed cost range not published $1,591–$1,802
ENERGY STAR certified yes not matched
Refrigerant R-134a, GWP 1430 not filed
On the market since 2021-01-31 not filed
DOE CCD · 2026-09-19

What it costs to run

FRIEDRICH PRO H40 T2 RH310BM: 928 kWh a year Lennox WHES040T45TD240S****: 3,531 kWh a year

FRIEDRICH PRO H40 T2 RH310BM — 928 kWh a year Lennox WHES040T45TD240S**** — 3,531 kWh a year

FRIEDRICH PRO H40 T2 RH310BM is 2,603 kWh a year lower than Lennox WHES040T45TD240S****.

DOE CCD · 2026-09-19

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Enter your ZIP to price both units on the same rate where you live.

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 FRIEDRICH PRO H40 T2 RH310BM if running cost matters most: it uses 2,603 kWh less a year on the same test.
  • Pick the Lennox WHES040T45TD240S**** if it is the one you can get installed sooner or for less — on the filed figures it has no advantage over the FRIEDRICH PRO H40 T2 RH310BM.
  • Neither if your household's busiest hour needs more than 60 gallons of hot water — neither lists more. Check whether a 40-gallon heater is enough.

Each model on its own

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