No, covering your outdoor AC unit is generally unnecessary and can cause problems:
Why not to cover:
Units are designed for year-round outdoor exposure
Covers trap moisture, leading to rust and corrosion
Small animals may nest inside, damaging components
Blocks ventilation, creating mold growth
Homeowners forget to remove before starting system in spring
What you should do instead:
Clear leaves and debris around unit
Trim vegetation 2 feet back from all sides
Ensure unit sits level on pad
Have professional maintenance before cooling season
When covering makes sense:
Extremely harsh winter climates with heavy snow
Areas with significant falling debris (tree canopy)
Use breathable cover designed for AC units (not tarp)
California winters rarely justify covering. Your outdoor unit will be fine without intervention.