When selecting PTAC units, you must prioritize the Energy Efficiency Ratio (EER); look for units with an EER of 10.0 or higher to ensure long-term operational cost savings. Ensure the cooling capacity (measured in BTUs) matches your room size, typically ranging from 7,000 to 15,000 BTU. Additionally, verify the noise level (dBA), as high-quality units should operate below 50 dBA on low settings to ensure guest comfort in hospitality settings. Lastly, confirm the use of R-32 or R-410A refrigerants to meet modern environmental standards.