There are six main questions that need to be considered when deciding to either replace or repair your heating and cooling system.
Age. How old is your system? If you system is more than ten years old, it may be wiser to invest in new, higher efficiency equipment, which could cut your energy costs by as much as 40%.

Efficiency. What is the efficiency level of your current indoor weather system? Unfortunately, replacing parts of your old system will not improve the efficiency. If the energy savings of using a higher efficiency system will cover all or part of the cost of investing in new equipment, you should seriously consider replacement of the old system.

Condition. What is the overall condition of your system? If your system is in solid condition, it could be wiser to simply repair it. But if your system breaks down often, you should consider replacing it.

Need for more power. If you need more warmth in the winter or cooling in the summer, it may simply be a matter of needing more heating or cooling capacity. The addition of a room of added windows can often put greater demands on a house's comfort systems.

Cost of Repair. How much is it going to cost to repair the unit versus replacing it? How much more money is it worthwhile to put into the old furnace? If the costs of repair and replacement are close, then it is a pretty easy decision.

Warranty. A new unit is covered by a warranty, and the existing one is not. Many new furnaces and air conditioners today have extensive manufacturer's warranties.