Several factors affect the cost of AC replacement. The size of your home and the capacity of the AC unit required are primary considerations. Larger homes need bigger systems, which increases costs. The type of air conditioner, such as a central unit or ductless system, also impacts the price. Additionally, upgrading to a more energy-efficient model or adding features like smart thermostats can raise the cost. Lastly, labor fees and any necessary updates to existing ductwork or electrical systems play a role in the final cost.