Rheem 88H40*
0.81 UEF DOE CCD · 2026-09-19No A–G grade: Fewer than 8 models share this heater type, fuel and draw pattern, too few for a fair A-G scale.
A short tank built to sit under a counter, low draw pattern (a one- or two-person household).
If you are checking the Rheem 88H40*, an under-counter short tank, it uses 2,771 kWh of electricity a year. That is at the low draw pattern, the standard daily hot-water usage DOE tests against, for a one- or two-person household. It has no class median comparison, because too few models share this class.
Energy use per year
2,771 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.
Not published: Class comparison
Too few models share this heater type and draw pattern for a fair class median, so no comparison is shown.
The yearly energy figure above stands on its own and does not depend on the class.
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
- 0.81 DOE CCD · 2026-09-19 Compared only with other models registered as a short tank built to sit under a counter 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
- 50 gal DOE CCD · 2026-09-19
- Rated Storage Volume the tank size in gallons
- 36 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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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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Every Rheem model on file
What this brand files, by heater type.
UEF 0.81 Price it on your ZIP
The registry lists a UEF, the ratio of hot water delivered to energy used, of 0.81 for the Rheem 88H40*. The registry does not list annual energy use. This site computed 2,771 kWh from that UEF and the DOE test's daily hot-water draw for the low draw pattern. The fuel is electricity, and the data source is DOE CCD, retrieved 2026-09-19. The figure holds only at that test draw. A household that uses more or less hot water than the test assumes will use a different amount of energy. The calculation method explains how the yearly figure and the yearly cost are derived.
The tank has a rated volume of 36 gallons. Its first hour rating, the gallons of hot water available in the first hour from a full tank, is 50 gallons. The low draw pattern corresponds to a one- or two-person household, so the 2,771 kWh figure describes that level of use. It does not show whether this tank covers a larger household's busiest hour, and the data gives no figure for that. The water heater selector filters by fuel, space and size if the household or the space differs from these conditions.
Running cost is not stated here, because it depends on your own electricity rate. Multiply the 2,771 kWh by the price your utility charges per kilowatt-hour to get a yearly amount. The cost calculator does this from your ZIP code. An installed price range is not published for this model, because its ratings lie outside the range the cost database was fitted on. The range is not stretched past it. Nor is the model compared with a class median, since too few models share this class and draw pattern. To look at other units in the same class, search by model number for a same-class replacement, starting from 88H40*.
DOE CCD · 2026-09-19