Here are a few common reasons why you may feel uneven temperature between floors:

- Ductwork needs to be properly sealed.

- The system isn't sufficient for the size of your home.

- Something may be restricting air flow.

Things You Can Do To Fix This Problem

Have your home's ductwork inspected by a heating and cooling technician.  Having air leaks or improperly sized ductwork can cause issues with efficient heating and cooling.

Add a ductless split system upstairs.  Although this is a more expensive solution, it may be one to consider.  Ductless air conditioners generally cost about $2,500 per unit and can work well for this.  These smaller room-based units pass cold air through the small air handlers which are mounted on the wall.  This solution may work well for floor plans with larger spaces on the second floor.

Adding a Zoning control system is also a great alternative to adding another ac unit.  Temperature can by independently set between floors.  These types of systems are easiest to install during new construction but can be added existing homes depending on how your existing ac system is currently setup. 

HVAC upgrades you not only help you stay cool during the summer but also can make for a great way to increase the value of your home.  If ever in the market to add or replace your current air conditioning system consider going with an energy efficient system.  HVAC manufactures have come a long way over the years to build stronger more efficient models that can last for years to come.