The cooling capacity of an air conditioner is measured in BTUs (British Thermal Units) per hour. A 12,000 BTU air conditioner is generally considered suitable for cooling a room or area of around 400-550 square feet. However, the actual effectiveness of the air conditioner depends on various factors such as the climate, insulation, number of windows, ceiling height, and heat-producing appliances in the apartment.
A 12,000 BTU air conditioner would likely be sufficient to cool a 400 sq ft apartment in moderate climates with average insulation. If the apartment has good insulation and few heat-generating appliances (like ovens, stoves, or multiple electronic devices), the air conditioner might be even more effective.
On the other hand, if the apartment is located in a very hot and humid climate or has poor insulation, the 12,000 BTU air conditioner might struggle to cool the entire space efficiently. In such cases, the air conditioner may run continuously and still not achieve the desired cooling level.
To ensure the air conditioner is appropriately sized for your apartment, it's essential to consider the factors mentioned above. If you're unsure about the appropriate size or have specific cooling needs, it's a good idea to consult with an HVAC professional who can help you choose the right air conditioner for your space.