What a written estimate should include
A good written estimate leaves very little room for surprises.
The problem in plain words
It should say what is wrong, such as "failed capacitor on outdoor unit," not just "repair system."
Every part and its price
Each part should be listed with its price, and whether it is new, used or rebuilt.
Labor
It should show either the flat-rate price for the job or the hours and hourly rate.
Refrigerant details
If refrigerant is added, ask the estimate to show the type, the amount and the price per pound. Adding refrigerant over and over usually means there is a leak that should be found.
Total and limits
It should give a total and say whether the price is fixed. If it is only an estimate, ask it to state that no extra work will be done without your approval.