If you use one of the rooms in your home as an office, you may be able to get a percentage off that as well. For instance, if you add central air conditioning to your entire home and your office comprises 15% of the rest of your home's space, you can deduct 15% of that total cost. You can find more specific information about that here.
There is another way that you can take a home office deduction, too. The simplest version of this allows you to take $5 per square foot of your home office up to 300 square feet for a maximum $1,500 deduction. Again, the home office needs to only be used for your business.