This was fixed in Patch 1.54.120.
All options on the shower are gray, although I bought a shower that’s supposed to work off-the-grid.
The new option Take Quick & Tepid Shower is missing for energized Sims.
Für Sims in energiegeladenen Zustand fehlt die neue Option Schnell und lauwarm duschen.
Wait until your Sim is no longer energized. Then you can take a shower.