You could, but the idea is to only heat water when necessary (there isn’t enough hot water and you need to take a shower), keeping it hot all the time is wasteful.
Running a thermostat 15-30 minutes before the hot water is needed would only consume electricity if the water is not already hot. You probably want a well insulated accumulator tank with one of these systems to not lose the energy produced as well.
Couldn’t you just have a thermostat on the tank
You could, but the idea is to only heat water when necessary (there isn’t enough hot water and you need to take a shower), keeping it hot all the time is wasteful.
Running a thermostat 15-30 minutes before the hot water is needed would only consume electricity if the water is not already hot. You probably want a well insulated accumulator tank with one of these systems to not lose the energy produced as well.