Yes the total sf matters. Unless you have a large part of it closed off to HVAC you are paying to heat/cool 5500 sf.
What is your insulation/window quality? Do you have a lot of insulation? Do you have double pane or thermal windows? If it’s new construction you’ll meet current title 24. But if it’s older, there’s probably a lot of places you could invest to reduce your energy bill.
Also 3 fridges… Could you move some of the beverages from the beverage fridge to the regular fridge – so that only one fridge gets open/closed a lot?
We’ve knocked about $10/month off of our bill by changing our habits with respect to power plugs for various devices – cell phones, kids NDS’s, etc… We only plug in the charge when it’s in use. (We used to leave it plugged in – but disconnected from the device when not charging.) We also unplugged the things that don’t get daily use but in their “off state” where really on, waiting for the remote signal… this included our dvd players, one of our stereos, the kids wii. (I only let them play it on the weekend for homework reasons. I’m a mean mom.)