According to toller :
I'd persuade the wife to run the dishwasher before leaving. Kill the
power to the HWT when she starts it.

Yes, I even installed a switch on the water heater for that purpose

When the dishwasher cycle ends, turn off the water feed to the HWT.

I'm not fond of killing power to the pump - you might lose prime.

Prime has never been a problem; it always pumps up in a minute or two.

The tank is about as likely to leak under power as not. So, if you're
concerned about long-term leaks, shutoff the water to the HWT OR turn
off the pump. Either/or.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.