Most central air conditioning units last about 20 years. Even if your air conditioner is only 10 years old, you may save 20-40 percent of your cooling energy costs by replacing it with a newer, more efficient model. A new roof, properly installed, can provide a strong seal against the elements and lower your heating costs. Additionally, dark roofs absorb heat and this can raise you cooling costs in the summertime. If you choose a lighter colored roof, you can save money on air conditioning as well.