Turn off? In what way? If power is still going to the unit but you've turned off the thermostat, the electronics of the HVAC are still active.We turn off the HVAC during electrical storms. We've lost one unit about 15 years ago, and for the cost, I'm willing to put up with a sweaty night to be able to keep it the rest of the time without spending lots of money to repair. And the added hassle of waiting for the repair companies to get to us (as usually we weren't the only ones dealing with issues).
For us, even turning off the thermostat does not disable the HVAC. Because of the house build (very well sealed) and weather here in Central Texas, HVACs in the newer houses (can't speak to the older houses) are set up to circulate the air via its fan every so often if the HVAC hasn't run the AC or the heater during a preset period of time. I would have to flip the breaker or turn off the switch in the antic to completely remove the HVAC from the electricity.