The answer to 'how much to replace air handler' is that the cost can vary significantly depending on several factors. Typically, a full air handler replacement can range from $2,000 to $6,000 or more, installed. The specific price will depend on the size and efficiency of the new unit, the complexity of the installation, and any necessary ductwork or electrical work required.
Other factors that influence the cost include the brand, features, and warranty of the new air handler, as well as the labor rates in your local area. It's important to get multiple quotes from licensed HVAC contractors to ensure you get the best value for your home.