How to Choose the Ideal Humidifier Capacity

How to Choose the Ideal Humidifier Capacity

Choosing a humidifier for your entire home can be confusing, especially if you’ve previously used only single-room units. Since it’s important to invest in a humidifier that can efficiently humidify your home, we’ve put together this guide to help you out.

What is humidifier capacity?

Humidifier capacity is how much water the humidifier can hold at a time. To calculate the ideal capacity of the humidifier, consider the dimensions of the humidifier (as this directly correlates to the capacity), and the dimension of the room. In general, the capacity of a humidifier ranges from 0.5 to 6 gallons.

It’s worth noting that the capacity is proportionate to the number of times the homeowner will have to refill the humidifier. For instance, if the humidifier has a capacity of 2.5 gallons, that means its output (the amount of moisture the unit can release into the air) is 5 gallons per day (GPD). For a five-gallon humidifier, you’ll have to refill the water every twelve hours. In other words, the greater the capacity, the fewer times you’ll need to refill the humidifier.

What should you consider when buying a whole-house humidifier?

A whole-house humidifier or central humidifier is attached directly to the water source so it can constantly supply moisture. This type of humidifier is also part of the home’s heating and cooling unit or HVAC. Here are a few factors to consider when purchasing a central humidifier:

#1 GPD

The GPD measures the amount (in gallons) of moisture a humidifier can put into the air per day. In general, a humidifier that’s rated at 2.0 GPD is enough for a room that’s not more than 500 ft2. Meanwhile, a humidifier that’s rated at 3.0 GPD is sufficient for a room that’s not more than 800 ft2. Spacious homes that measure more than 2,000 ft2 would need a humidifier with a GPD of 10.0 or greater.

When considering the GPD, don’t forget to account for the load. The load is the amount of humidity that your family generates in a day, which is typically two gallons of water. Determine the load and then deduct it from the total GPD indicated on the unit.

#2 Building Tightness

Another factor to consider is the tightness of the building. Tight buildings are those with doors and windows that have been weather-stripped, while loose buildings include those that were built in the 1930s or later. It’s important to consider the building’s tightness because it impacts the number of air changes per hour (ACPH). A loose building would naturally lose more air, and in turn, need more humidity.

#3 Ceiling Height

Whole-home humidifiers often indicate the ideal ceiling height, so be sure to check those when looking at units. If the humidifier doesn’t indicate the ceiling height that they used, it’s safe to assume that it used an eight-foot ceiling to calculate the GPD.


If you aren’t sure which whole-home humidifier to go for, get the professional advice of an HVAC technician at Beeson Mechanical Service. We can recommend the ideal furnace humidifier for your home, as well as help you narrow down your choices by brand. Call us at 317-535-9338!