We have it so when you turn on the bathroom light it starts the recirculation pump. We use a different amount of time depending how far you are away from the tank. This really helps that so no water is wasted here. We waste less water than a most tank heaters.
The hot water pipes and the return lines are all insulated.

I was going to wire it in on the light switch or put the circulation pump on a count down light switch timer.

I would in your place have installed several tankless water heater