Sooner or later you will replace your heating and cooling system. Furnace and heat pump air handlers have a useful life of about twenty years. Air conditioning condenser useful life varies between five and fifteen years. The condenser is the outdoor unit. If you need to replace your heating and cooling system, here are some tips to ensure that your system provides safe, energy efficient, and green operation. Install new equipment that has the highest energy efficiency rating that you can afford. The energy savings from a high efficiency system will often save you more over the system's life than the additional cost. Higher efficiency systems qualify as green and add value to your home. They may also qualify for government and utility rebates.