Nobody wants to do it, but eventually you have to.  These tips will help you decide if it is time to bite the bullet and pony up the dough. 

• If your air conditioner is more than ten years old.  Great advances have been made in ten years that will save energy and money.  If you are replacing just the unit, have all your ducts checked to see if they need to be replaced or repaired as well.  That money will be wasted if it all leaks out into your attic.

• If your equipment needs frequent repairs and your energy bills are going up.  Your electric company can tell you, and you can often check online, what your energy use was this month and what it was this month last year and the year before.

• Some rooms are hot while others are cold.  This is usually a sign of duct problems or poor insulation.

• Your home has humidity problems.

• Your home has excessive dust.

• Your cooling system is really loud/noisy. 

If you are experiencing any of these problems it is time to call a professional and get your system inspected, if not totally replaced.  If it is time, you will be glad you did because it will start saving you money right away and the unit usually pays for itself in the long run.  Make sure to ask about any rebates and tax credits that might be available to you.  Or you can find many at:
http://www.energystar.gov/