Howdy RFheavy, I have a 14,000 BTU A/C unit (a SPT) and it works very well in my living room. The hot air exhaust (from the condenser coil) should be vented COMPLETELY out of the room that the tent is in, other wise, the heat will remain in the room keeping it hot and making the tent hot as well. The grow tent still needs fresh air to be circulated into and around inside of the tent. The heat extracted from the lamp should be vented outside of the room to get ant reduction of the heat generated by the lamp. You may need to move the tent closer to a window so that the exhaust tube will reach. If You have to add an extension tube to reach a window, use a smooth sided tube (A/C or heater vent pipe from hardware store) and it would be best if an inline fan is added to prevent back pressure to the A/C unit.