A. O. SMITH ENS-40W 1**
0.88 UEF DOE CCD · 2026-09-19Grade G: where this UEF sits among the 163 models in its class, lowest (G) to highest (A). A position, not an official label. How the grade is set
An electric tank, low draw pattern (a one- or two-person household).
For a one- or two-person household, the A. O. SMITH ENS-40W 1** uses 2,550 kWh of electricity a year. That figure is for the low draw pattern, the standard daily hot-water usage DOE tests against. It is 111 kWh above the class median of 2,439 kWh.
Energy use per year
2,550 kWh a year
Computed by this site from the registry's UEF and the federal test's daily hot-water draw for this draw pattern. What it costs depends on the electricity rate where you live.
That is above the median of 2,439 kWh for the 163 models registered in the same heater type and draw pattern; it ranks 158 of 163, lowest energy first.
Solid line: this model (2,550 kWh). Dashed line: the class median.
Min 724 kWh Median 2,439 kWh Max 2,550 kWh
What it costs to run where you live
What the registry files
- UEF (Uniform Energy Factor) how much hot water you get for each unit of energy the heater uses
- 0.88 DOE CCD · 2026-09-19 Compared only with other models registered as an electric tank at the low draw pattern.
- Draw Pattern the standard daily usage profile DOE tests the unit against
- Low DOE CCD · 2026-09-19
- First Hour Rating how many gallons of hot water the unit can deliver in one hour, starting from a full tank
- 41 gal DOE CCD · 2026-09-19
- Rated Storage Volume the tank size in gallons
- 37 gal DOE CCD · 2026-09-19
What it costs to install
Not published: Installed cost range
This model's UEF lies outside the range NLR REMDB's cost model was fitted on, and the range is not stretched past it.
The annual energy figure on this page does not depend on this range and is unaffected.
Safety record
No CPSC recall names this model.
Checked against the CPSC recall database. CPSC does not publish a model-level match for this product category, so this list is curated by hand from the manufacturer's recall filings.
CPSC · 2026-09-24What these figures mean
How this compares
The closest models in the same class — same fuel, type and draw pattern.
Keep going
How every figure on this page is calculated
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Find what replaces your water heater
Enter the model number off your old unit and see what is on file today, with the yearly cost difference.
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Find a water heater that fits
Three questions — fuel, hot water need, install space — narrow every model on file to the ones that fit.
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What a water heater costs to run
Prices a unit's efficiency against your own utility's filed tariff for your ZIP code.
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Is a 40-gallon water heater enough?
Answered from what models in this size actually file.
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Water heaters
Every model on file with the Department of Energy, by heater type.
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All electric resistance tank water heaters
Electric tanks that file a UEF below 2.0 — heated by elements, not a heat pump.
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Every A. O. SMITH model on file
What this brand files, by heater type.
UEF 0.88 · Grade G Price it on your ZIP
The figure of 2,550 kWh comes from this site, not from the registry. It uses the registry's UEF, the ratio of hot water delivered to energy used. The registry lists a UEF of 0.88 for this model. The site combines it with the DOE test's daily hot-water draw for this draw pattern. The source is DOE CCD, retrieved 2026-09-19. Among the 163 models registered as an electric tank at the low draw pattern, the median is 2,439 kWh. This model is 111 kWh above that median. It ranks 158th lowest in energy use of 163, in the highest quarter of its class for energy use. The method is described on the page about how the annual cost is calculated.
This figure applies only to the low draw pattern, which describes a one- or two-person household. The first hour rating, the gallons of hot water available in the first hour from a full tank, is 41 gallons. The rated volume is 37 gallons. The data give no annual energy figure for any other draw pattern. A household that matches the low draw pattern can use 2,550 kWh as the reference for this model. A reader who needs the lowest energy use in the class should note the rank of 158th of 163. The water heater selector by fuel, space and size lets you filter other options.
Running cost is not stated in the text, because it depends on your own utility electricity tariff. The cost calculator on your own ZIP applies your rate to 2,550 kWh of yearly electricity use at the low draw pattern. At any one rate, the yearly cost difference from the class median equals 111 kWh multiplied by that rate. An installed price range is not published for this model. Its ratings lie outside the range the cost database's model was fitted on, and the range is not stretched past it. The energy figures reflect the retrieval date of 2026-09-19.
DOE CCD · 2026-09-19