I have a multi level home, and it's set up in 3 zones so I can set my thermostat for each zone, up to 4 periods per day, for the whole week(HVAC tech says they now claim this method really doesn't save $). We are comfy at 68 for heat, so if other zones aren't being used for a period, what is the lowest I can set them without causing a problem? Is it efficient to have different temps set for each zone? Will it harm the system? Or should we keep all zones and periods set at 68?

Once summer hits, what should we do there? Our comfort level set for air conditioning to go on after room hits 77 or higher. But some days we are not in the house all day and summer is different than winter, in winter, I would not want to turn the heat totally off, in summer though, is it necessary to run AC if we're not even home?

Some people play with thermostats all the time, up, down, etc, while others claim setting ot and leaving it constant.

I can't answer all of your questions until I know what kind of heat you have. Hot water, forced hot air, steam? How is the zoning accomplished? No you don't need to run your ac when you are not at home. However, if you come home from work and the house is too hot you will have a difficult time cooling the home. Once the house is hot everything in the home is hot, not just the air. The wood, fabrics, flooring, everything has become warm and will try to hold heat. The tech who said it isn't cost effective may or may not be correct. A great deal depends on your insulation factors and the efficiency of your equipment.

Use each zone like it had its own system. I would not let it go cooler than 55 in the winter or higher than 80 in the summer. All zones have a common return air so you are moving air around even though a zone may not be calling for heat or air. If your not using one part of the house why heat or cool it. That's how you save your money.

It's heat pump and central air. I think my thermostat has a feature where you can shut a zone off if not being used and it has a protection where it won't allow the room to get colder than 55 or hotter than 80. I agree about not letting it get too cold or hot, because the system then has to catch up to get it where you're comfy when you want it to be comfy. For winter, as I said we set at 68, but say at night, a zone isn't being used, I was going to set it down to 65 or 66. So when we want it back at 68, it would have to go up 2-3 degrees, and I notice at times if it needs to go up 3 degrees or more, the auxiliary kicks on, and I don't think that is as efficient? That's why I wanted to know how much of a difference in degrees I should go for zones not being used if when we want it comfy that would be 68?