You must buy, within the correct type and capacity, the highest air conditioner in the EER, provided it is not an exorbitant expense. Buying a device with less EER and more economic usually is not usually a very advantageous option. Do not trust the offers and always look for a brand of trust and quality. If you buy an unknown brand system in the long run can be more expensive.
Of course, common sense is the best rule to apply although there are some basic guidelines:
Check different prices and opinions on websites.
Use buying systems between different models and brands.
Check the manufacturer's website and verify the EER and BTU / hour values.
Ensure the existence of a service network.
Note the Noise
Factor in the Window Location
Install it Correctly
Check Filter Location
Watch the Warranty