Ariston ENS40L-*
Ariston ENS40L-* is in the DOE listing as of Oct 19, 2026.
- Electric storage water heater
- 1 listed model
ENERGY STAR certification does not cover this type of water heater.
Its figures are also listed under AMERICAN STANDARD WATER HEATERS ENS40L-*.
Certified figures
- Storage volume
- 36gallons
- UEF
- 0.92Uniform energy factor
- First-hour rating
- 46gallonsHot water in the first hour
Your busiest hour
Change your hourCertified figures by listed model
| Model number | Storage volume (gal) | UEF | First-hour rating (gal) | Recovery efficiency | Draw pattern |
|---|---|---|---|---|---|
| ES40S-S* | 36 | 0.92 | 46 | 98% | Low |
UEF is the uniform energy factor. A dash means the model has no such figure.
It holds 36 gallons in the test, 4 gallons less than its 40-gallon sold size. Starting full, it gives 46 gallons of hot water in its first hour of use. That is 10 gallons more than its tank holds, since it reheats during the hour. In the first hour, 368 of the 477 electric storage models give more hot water. The median electric storage model gives 55 gallons in its first hour.
In the test, 8% of its energy does not reach the hot water (UEF 0.92). The daily hot water use in the test, called its draw pattern, was low. Of 157 electric storage models with the same draw pattern, 12 have a higher UEF and 76 a lower one. On its draw pattern, its UEF is also the median electric storage UEF. When it reheats water in the test, 98% of the energy it uses ends up in the water.
All of its test figures are shared by 2 other basic models. Those basic models are sold with AMERICAN STANDARD WATER HEATERS and Lennox as their brand names. For the full group, see the AMERICAN STANDARD WATER HEATERS ENS40L-*.
Also listed as
They carry every figure in the table above.
- Every Ariston basic model
- Every 40-gallon electric storage water heater
- Every electric storage water heater
Not covered
- Advertised figures. We have none on file for this model.