We recently finally had smart meters installed, so I have switched to Flick Electric to supply our power, whom use the smart metering data to automatically charge much lower rates for any power usage between 11pm and 6am.
Thus it makes economic sense to move as much of our household electrical load to these times, to enable this I have installed a high current time switch to the electrical feed to the upper HWC element, this provides adequate hot water for 4 showers and halving the cost.
In our situation the lower element is normally turned off as the bottom half of the cylinder is solar heated and on average this supplies >85% of our annual hot water, except in winter, cold rainy days like today.
Further power hungry modern dish washers and washing machines have inbuilt timers aleady fitted and can be simply programmed to run during the early morning hours, thus saving more money.
So installing a time switch to your HWC is a great way of saving money, providing your energy supplier charges you less for power consumed at night, we didnt have to switch to any day\night plans nor get a seperate night meter, the smart meter does it all, so for a change its a winning situation.