1. Who pays for electricity 2. Is ac system servicing just that one apartment 3. Does the lease say it is an air. conditioned apartment and who is responsible for maintaining the ac equipment 4. If tenant pays for electricity used how cold they want it is their business. Constant ac use at low temp settings can result in freeze ups which will cause higher temperature and can damage ac equipment. Your tenant should be aware of this issue and put on notice that freeze up damage,....including resulting condensation water damage is their responsibility at significant cost. 5. You may have to get an ac service man to come out and check the system for proper performance.