Do check that your heater isn’t doing something ridiculous. A while back I helped someone debug a Mitsubishi Electric system on which the installer had set the fan speed control to high instead of auto (it’s an easily accessible setting on the thermostat). I forget exactly how much power was saved, but IIRC it was well over 30kWh/day.

I don’t know where all that energy was going. I expected some improvement but not anywhere near that much.