ORBEK HW100
ORBEK HW100 is in the DOE listing as of Oct 19, 2026.
- Gas tankless water heater
- 2 listed models
Not listed as ENERGY STAR certified on Oct 19, 2026.
Its figures are also listed under Mizudo FDG-CS100.
Certified figures
- Flow at a 67°F rise
- 2.4–2.5gallons per minute
- UEF
- 0.81Uniform energy factor
The 2 listed models differ. A range runs from the lowest figure to the highest.
Your fixtures at once
Change your hour and flowFlow where you live
Colder incoming water needs a bigger rise, so the heater gives less flow.
- 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 2.3 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.
Certified figures by listed model
| Model number | UEF | Flow at a 67°F rise (gal/min) | Recovery efficiency | Draw pattern |
|---|---|---|---|---|
| HW100A0W-LP | 0.81 | 2.5 | 82% | Low |
| HW100A0W-NG | 0.81 | 2.4 | 81% | Low |
UEF is the uniform energy factor. A dash means the model has no such figure.
Its flow at a 67°F rise is 2.4 to 2.5 gallons per minute, by model number. The median gas tankless model heats 4.8 gallons per minute by 67°F. Among 487 gas tankless models, 476 give more flow at a 67°F rise.
On Oct 19, 2026, this heater was not listed as ENERGY STAR certified. In tests, 81% of the energy it uses ends up as hot water (UEF 0.81). The daily hot water use in the test, called its draw pattern, was low. Its UEF is lower than that of 5 of the 9 gas tankless models with its draw pattern. For its type and draw pattern, the median UEF is 0.82.
It is the basic model for HW100A0W-LP and HW100A0W-NG. Its test figures match those of one other basic model. The brand name on that one is Mizudo. For the full group, see the Mizudo FDG-CS100 page.
Also listed as
They carry every figure in the table above.
- Every ORBEK basic model
- Every gas tankless water heater certified below 4.0 gallons per minute
- Every gas tankless water heater
- The most-searched gas tankless models side by side
Not covered
- Advertised figures. We have none on file for this model.