Gigantic House Means High Heating and Cooling Costs

A year or so ago, my brother bought a gigantic house. I find it so strange, as I think he should be downsizing, not moving into a bigger place, but there is no convincing him of that. Instead of moving into a townhouse or something, he sold his rather big house and bought a gigantic one. Mind you, he lives all by himself. Anyway, he says he thought the house was a good buy, so he got it, and I guess whatever makes him happy is fine with me. Anyway, the house is 6000 square feet and has two stories and either 5 or 6 bedrooms. But one thing he has noticed since moving in is that a gigantic house means gigantic heating and cooling costs. His utility bill is astronomical, in my opinion. Anyway, he admits that the a/c is too expensive, so he recently called in an HVAC specialist to give him some advice on how to make the heating and cooling more efficient and what to do to be good to the environment and also good to his wallet. The HVAC guy gave him several options to look at, and I think my brother has decided to get HVAC with zone control. They will split the home into areas, or zones, and he can adjust the thermostats for each zone as appropriate. If no one is going to be upstairs, there is no need to run the a/c full blast. When he has guests, he can turn the thermostat down for them to keep them comfy in the summer or use the furnace to keep them warm in January without breaking the bank.
Heating dealer