Stop closing vents off or blocking them in rooms not used. This will not reduce the load on your HVAC system and will cost more on the electric bill.
If you have a central air system the pressure load is balanced for the ductwork throughout the house. Blocking vents can impact how the system breaths (inhales and exhales) air. Doing this will cause to be thrown out of balance. This results in your compressor working harder, running longer, more repairs, and early compressor failure. I advise leaving all vents open. Doing this the air will be circulated throughout your whole home at a balanced rate. Which makes the whole house comfortable.