The cooling capacity of an air conditioner is typically measured in BTUs (British Thermal Units) per hour. However, the cooling area that an air conditioner can effectively cool depends on various factors, including the climate, insulation, windows, and other environmental conditions. As a result, it is challenging to determine the exact square footage an 18,000 BTU air conditioner can cool without additional information.
As a general guideline, a rule of thumb for air conditioners is that 1 ton of cooling capacity (12,000 BTUs per hour) can cool approximately 400-600 square feet of space. Using this rule, an 18,000 BTU air conditioner would have a cooling capacity equivalent to 1.5 tons of cooling. Therefore, it might be able to cool around 600-900 square feet of space effectively.
It's essential to consider other factors when selecting the right size air conditioner for your space, such as room orientation, ceiling height, heat-generating appliances, and the number of occupants. If you need a precise estimate, it's recommended to consult with a professional HVAC technician who can perform a proper load calculation for your specific environment.