Spare yourself the expense of hiring a professional to clean the outside air conditioning coil of your HVAC unit. But you may want to call a professional to clean the inside coil.
Before you clean the outside coil, turn off the power. The switch should be next to the outdoor unit. Use a hose to clean the unit of dirt and debris. Do not use a power washer.
Cleaning the indoor coil is more challenging. Turn off the power switch near the furnace or at the main breaker panel. After removing the cover plate from the coil, vacuum the coil using a soft brush on your vacuum cleaner. Take care not to damage coil fins or move the coil. Empty the drain pan under the coil. Clear the opening to the condensation drain line. Replace the cover and restore the power.
Some contractors use a foaming coil cleaner for the outside condenser, and a non-foaming cleaner for the inside coil. The cleaners can generally be found at some hardware stores or plumbing suppliers.