I'm really surprised at some of your utility bills. We're in 2bdm flat and 3 AC units. the living room AC unit is kept on 24 hours for the dog (at "efficiency setting" around 23 deg). we cook at home, use a clothes washer (7kg model), use 2-3 dehumidifiers as needed. DLNA server always-on. our E-bill is about 200-300.
mind you, i do try to prevent leakages (doors and windows) with insulation tape.