If the total cost was less than $2500, you can elect to expense it (write it all off). If you bought the material and paid for the installation separately, and either or both was less than $2500, you may expense that part.
There's another possibility. You may expense it if the cost of all repairs, maintenance and improvements is less than or equal to the smallest of these limits:
-2% of the unadjusted basis of your building or
-$10,000
