How do you keep your upstairs cool? I have two units, and keep the lower level two degrees lower than upstairs. Downstairs is always cool, bit the upstairs until runs a lot and struggles to get below 77 degrees.

The thermostat does sit on the side of the house that gets most if the sunlight throughtout the afternoon and evening, so that may not help the situation.

Do any of you have a similar issue? TIA