A humidifier's capacity, or the amount of moisture it can dispense in a given time, should match your particular household's needs. The capacity is measured as gallons per day of operation. One method that is used to determine the correct-size humidifier for your home is multiplying the total floor area in square feet by the ceiling height.
Consider not only the purchase price of the unit. but also the operating and maintenance costs. Some products consume more energy than others, so choosing a model that is right for your home and budget is extremely important.