My electric utility company sent me a graph of my home's electricity usage over time as shown in the picture below. My home beats what the company considers as efficient homes in the neighborhood when the average temperature is below ~50F. As the temperature increases above ~50F my home becomes increasingly inefficient, relatively speaking.
I'm puzzled by this. Can anyone help me understand what part of my house I need to improve? Does this mean that my home's insulation is OK, but A/C system is not? Or, does it mean that heat enters my house easily but does not escape easily, meaning insulation is good in one direction but not the other?
As reference, my house has centralized HVAC. Heating in my home is natural gas. The A/C is traditional, refrigerant-based, with the compressor located in an external unit. Most components of the HVAC system are about 20yrs old.