https://sunamp.com/en-gb/hot-water-solutions-thermino-range/
The phase change stuff has positives like taking up less physical space but it's also a much less mature tech than storing hot water.
In the UK there was a unfortunate trend of ripping out these energy storage devices and replacing hot water tanks with on demand electric hot water heating ( only heat the water you need ). And new builds often have no tanks ( as it saves space in the new tiny homes ).
Very short sighted in my view - a very simple way to store energy and everyone uses hot water directly.
One interesting case where "at the same time" actually does happen is overnight car charging. Some chargers are configured to start charging exactly when a cheaper tariff kicks in, which causes big transient issues for the grid. I think modern chargers have a random delay to help with that.
Here in the UK some electricity providers offer 'smart' charging (e.g. Octopus Intelligent Go).
In that situation the energy provider controls when to charge the car - e.g. you say "I want the car at 80% by 7am tomorrow" and the energy provider controls the timing of charges.
That's how my EV charges - I plug it in, and Octopus control it.
Benefit for me is that whenever the car is charging my entire home's use gets the overnight rate (even if part of the schedule is charged during the day).
Benefit for Octopus is they can use my car to balance grid demand / schedule the charge when it is most financially effective for them.
I can - at any time - override that logic if I just want it to charge at a specific time for whatever reason.
(I presume this sort of arrangement is becoming more common in other countries too)