On 30-Mar-2004, wrote:

What about heating elements that can be run at lower wattage (such as two
elements switched on in series instead of parallel) during idle times?
Do any tanks even have this capability?

It makes no difference in terms of overall energy use. If the wattage is
lower, they will have to be on longer to heat the water, so the duty cycle will
be longer. But the total energy going in has to equal the total energy lost
through the shell or the water will continue to get hotter or colder over time.
You could put in a 10,000 watt heater or a 100 watt heater and the energy use
over a period of time will be exactly the same. The only difference is how
long it takes to heat the water initially and how long it would take to reheat
the water after you use some.