Yes, but bulk of the demand is heat and industry, so you're quickly back to having to build a lot of "storage" in the form of buildings with high thermal inertia and spare capacity for production, so that you can keep the high energy plants idle at inconvenient times. Hard to say if that is more efficient than building actual energy storage.

Every little helps I guess, but getting people not to shower on cloudy days is not gonna move the needle materially.