Yes it is. Using a fan while using an air conditioner may help reducing the air conditioning bill. A ceiling fan will use the same principle which makes a windy winter day more colder then it actually is. By using your ceiling fan, you can use the air conditioner at lower settings, and hence preventing the usage of energy on the air conditioner. As ceiling fans comparetively do not consume as much energy as an ac, you will end up saving money on the energy bill.