Like almost every home in the world, your house is equipped with a heating or cooling system. This usually adds as much as 50% to the utility costs. This is pretty much, and it can get even more if your HVAC (Heating Ventilation and Air Conditioning) system is outdated.
Old systems can have leaks, improper insulation, and also eat a lot of energy.
Changing this system not only it will cut the costs but also you will feel a lot better in the summer and in the winter. They are also a lot more environmental friendly.
10 years old systems should be definitely replaced. On new systems you can also get some advantage of the federal tax credits that can go up to $1000-1500. Also the return of investment will be much bigger.