I run a 300 gallon tank with an 8 lamp T5 fixture. If your house has AC and you maintain the temperature say around 78 or below there should be no need to run a chiller. I don't need to run a chiller. I guess it also depends on the equipment you are running ie return pump, flow pumps, etc. Anything creating additional heat.
Fans across the water above the display or sump also help a great deal, but you'll need to add addtional rodi top off.