Model: Rheem 80 gallon electric model# model: XE80T10HD50U1.

I set my Rheem 80g to High Demand but can hear the fan/heat pump roaring. At High Demand, does Rheem sometime SIMULTANEOUSLY ACTIVATE the Heat Pump besides activated Electric Element??



  • 1
    Try contacting Rheem; I would expect both to sometimes run simultaneously in high-demand situations. Similarly, a hybrid car will sometimes draw power from both the engine/generator and battery at the same time.
    – Armand
    Commented Feb 25, 2023 at 19:42

1 Answer 1


Yes, it does.

From my manual (I have a similar Rheem HPWH):

Operational Modes:

Heat Pump Mode

This mode will heat with Heat Pump operation and will not use electric heat during typical heating and demand cycles. This mode has a low recovery but minimizes power consumption.

Energy Saver Mode

This mode will provide functional control operation resulting in water heater performance that meets Energy Star requirements. FHR (First Hour Rating) – exceeding the minimum of 51 GPH (Gallons Per Hour) and a minimum UEF (Uniform Energy Factor) of 2.0. As a result, compressor operation will be maximized and use of electric heat will be minimized.

High Demand Mode

This mode provides the highest recovery while still providing good energy savings. Water heater operates Heat Pump and Electric Heat simultaneously.

Electric Only Mode

This mode will heat with the electric resistance elements. This mode should only be used during filter and condensate drain maintenance periods. This mode will result in maximum power consumption. (See “Elec. Heat Override Time” in settings.)

Vacation Mode

This mode will allow duration setting between 1 and 28 days or set indefinitely with the “Hold” setting. Tank temperature will be maintained at about 65°F.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.