sizing new subpanel
I have 100A service. My main panel is full, but I want to run four new circuits:
2 x 20A circuits for bathroom GFCIs (biggest load - hairdryer on each)
1 x 20A circuit for bedroom outlets (biggest load - multiple window ACs)
1 x 20A circuit for finished basement (biggest load - fridge+TV)
The more significant loads in my main panel are:
2 pole 15A -central air handler
2 pole 30A - central air condenser
2 pole 30A - feed to garage fuse box
2 pole 30A - dryer
I was thinking of adding an 80A subpanel adjacent to the main panel to accomodate my new circuits. I have two 15A breakers that I can remove from the main panel to install the new 2-pole breaker for the subpanel. Does this make sense? Could I get away with a 60A breaker, which is cheaper, since the four circuits would unlikely draw the maximum 80A?
I was actually surprised the house had 100A service, considering it has central air, but we never had any power problems last summer. I'd like to upgrade to 200A service at some point, but I understand that it's a big expense.