American GPDNL-40 1**

It holds 38 gallons in the test, 2 gallons less than its 40-gallon sold size. Starting full, it gives 75 gallons of hot water in its first hour of use. Reheating lets it give 37 gallons beyond the 38 gallons in its tank. In the first hour, 443 of the 763 gas storage models give more hot water. Among gas storage models, the median first-hour rating is 78 gallons.

On Oct 26, 2026, this heater was not listed as ENERGY STAR certified. In the test, 30% of its energy does not reach the hot water (UEF 0.70). The daily hot water use in the test, called its draw pattern, was high. Among 434 gas storage models on its draw pattern, 111 have a higher UEF. For its type and draw pattern, the median UEF is 0.66. When it reheats water in the test, 77% of the energy it uses ends up in the water.

All of its test figures are shared by 3 other basic models. Those basic models are sold with A. O. Smith, Lochinvar, and State as their brand names. For the full group, see the A. O. Smith GPDNL-40 1** page.

In 2 states, 2 rebate programs may accept it.