You’ll have more Draw Calls if your objects are scaled (Something like Vector3 (1.0001f, 1.0001f, 1.0001f)). This can be a big problem if you are instantiating the same object a lot and need to keep your Draw Calls low.
When you instantiate the same object and your Draw Calls increase you can check the scale of your objects and make sure that they are not scaled.
There are some rules to follow to keep your DrawCalls as low as possible, you can read the full documentation about Draw Call Batching here: http://docs.unity3d.com/Documentation/Manual/DrawCallBatching.html