Energy saving box on an old whirlpool hot water heater
You need to have a conversation with your power company
Those &quot;energy saving boxes&quot; come in two kinds: one that turns off the water heater at certain times... and the other that qualifies you for a lower electricity tariff if the power company can interrupt your water heater at peak times.
The first type of box should simply go away. That's because of scientific discoveries that if tanked water heaters store water too cool, they breed bacteria including legionella.  Heaters need to be at around 60C to avoid this -- interrupting power and letting it fall to 50C or 35C can breed that bacteria bigtime.
For the second type, you need to have a tariff/rate conversation with the power company.  If they are willing to put you on the favorable tariff (or if they already have), they should help you maintain that controller.
What the power company needs it for is moments when power demand is nearly exceeding available generating capacity.  They have two choices:

Spin up standby generators called &quot;Peakers&quot; -- which are only used a few hundred hours a year, even though the mortgage runs 24x7x365.  As such, these power plants are murderously expensive.  Or...
Shed some load - this is most infamous in &quot;rolling blackouts&quot;.  Being able to command 10,000 customers' water heaters to take a 15-minute siesta will work just as well, and is much more civilized.

Naturally the power company gives you some financial incentive to do this.  Though it's also being a good civic citizen.