Do you want to keep your air conditioner cooling as it should?  

As a home inspector, I see lots of dirty air conditioner units. Air conditioner units must be able to breathe. It is vital that your unit allows as much air flow to pass by the coils as possible. Now you cannot stop all the debris from collecting on the outside of your air conditioner unit, but there are some things you can do.  

For example, if you have a dryer vent that is found near your air conditioner unit, be adamant about cleaning your dyers lint filter after every load so you capture more of the dryer lint. Because if you don't, some of that dryer lint will get trapped against your air conditioner. One other thing that you should do is to turn off your air conditioner while you cut your lawn. The grass clippings and other airborne debris will collect on the outside of the unit, blocking the needed air used to transfer the heat into the air. Think about this, if you were to try to breathe out of a straw, you would be able to, but you will have to work harder than you should to perform the task. So, when your air conditioner fins are dirty, your air conditioner will have to work harder and it will have to run longer to get the job done. This will increase the annual cost of cooling your home. 

A qualified tradesman should clean your air conditioner units yearly, as part of your HVAC maintenance program. This will also extend your HVAC system's life, cutting costs and making your home more comfortable year-round.