Rheem SPEX4208
Rheem SPEX4208 is in the DOE listing as of Oct 26, 2026.
It has a certified UEF of 0.97 and a certified flow of 0.4 gal/min at a 67°F rise.
Its certified flow is 0.4 gal/min at a 67°F rise, while Rheem advertises 2.0 gal/min, no rise stated (Read Oct 5, 2026), so a comparison at the same rise is not possible.
- Electric tankless water heater
- 1 listed model
ENERGY STAR certification does not cover this type of water heater.
Certified and advertised figures
- Flow at a 67°F rise
- 0.4gallons per minuteCertified
- Advertised flow
- 2.0gallons per minuteRheem, no rise stated
- UEF
- 0.97Uniform energy factor
Your fixtures at once
Change your hour and flowFlow where you live
The heater gives less flow when colder incoming water needs a bigger rise.
- Cold water
- Cold water must be at least 10°F colder than the hot water setting.
- Flow estimate
- The estimate uses the lowest certified flow among the listed models. It is about 0.4 gal/min at a 70°F rise.
Flow limits
- The estimate excludes the flow needed to turn the heater on, heat lost in pipes, and installation.
- Cold water from a well or long pipe run can differ from the temperature you enter.
- Without a stated flow limit, estimates for warmer water may exceed the heater’s actual flow.
Advertised and certified figures
| Figure | Advertised | Certified | Advertiser | Read |
|---|---|---|---|---|
| Flow | 2.0 gal/min, no rise stated | 0.4 gal/min at a 67°F rise | Rheem | Read Oct 5, 2026 |
Certified figures by listed model
| Model number | UEF | Flow at a 67°F rise (gal/min) | Recovery efficiency | Draw pattern |
|---|---|---|---|---|
| RTEH4208 | 0.97 | 0.4 | 97% | Very small |
UEF is the uniform energy factor. A dash means the model has no such figure.
It heats 0.4 gallons per minute of water by 67°F in the test. The median electric tankless model heats 0.7 gallons per minute by 67°F. Its flow at a 67°F rise trails 233 of the 337 electric tankless models.
In tests, 97% of the energy it uses ends up as hot water (UEF 0.97). In the test, daily hot water use was set to very small (its draw pattern). Of 272 electric tankless models with the same draw pattern, 37 have a higher UEF. For its type and draw pattern, the median UEF is 0.96. When it runs, 97% of the energy it uses reaches the water (its recovery efficiency).
There are 2 more basic models with the same test figures. Those basic models are sold with EEMAX and KWICKSHOT as their brand names.
Also listed as
They carry every figure in the table above.
- Every Rheem basic model
- Every electric tankless water heater certified below 1.0 gallon per minute
- Every electric tankless water heater
Not covered
- Changes to an advertised figure after the date beside it.