For central air-conditioning, you'll pay $3,000 to $5,000 and up for a 2,000 square foot home. A new furnace in a central heating system costs $2,500 to $7,500 or more. If you don't need ductwork, the cost of a new heating and cooling system can be significantly decreased. In cases where new HVAC duct is required, however, you might pay $1,000 to $3,000.