How Many Humidifiers Do I Need for My House?

So, you’ve determined that the air in your home is a tad too dry. You also fully understand why this is bad for your family and guests, as well as the home itself and items within it. For instance, you’re aware that low humidity levels are harmful to your health. It causes dry skin, can trigger cold and flu symptoms, and often worsens allergies and asthma.

You also know that your pets and plants need the right humidity levels to thrive and that your furniture and wooden items/surfaces would warp and get damaged if the humidity levels remain too low for too long. As a result, you’re planning to increase humidity levels in the home by buying a humidifier.

However, you don’t really know how many humidifiers would be enough. Is it one, two, or three humidifiers? Or do you need more? Also, do you need a humidifier for every room in the home, or can some rooms “share” humidifiers?

Definition and Purpose

To answer the above questions, you must first understand how humidifiers work and why you need them in the home.


A humidifier is an electrical appliance designed to raise the home’s humidity levels by introducing extra moisture in the various rooms. The appliance works by breaking down water particles into fine moisture, which is then pushed out of the humidifier and distributed throughout the home.

There are four main types of humidifiers, as follows;

  1. Ultrasonic humidifiers: Utilize high-frequency sound vibrations to break down water into fine particles. They are the most popular.
  2. Evaporative humidifiers: Feature a wick that also functions as a filter. The wick absorbs water from the tank, and a fan forces air through this filter to break down the water into mist.
  3. Impeller humidifiers: Rely on a rotating disc to fling water at a diffuser, which breaks the water into fine droplets.
  4. Steam humidifiers: Boil water to evaporation. The resulting vapor is then pushed out of the humidifier and distributed throughout the home.


However, the humidifier’s purpose isn’t just to add moisture to the home. It must add the right amount of moisture at the right rate to meet the house’s humidity needs.

The recommended indoor humidity for healthy living is 30% to 50%. Therefore, the humidifier’s main purpose is to raise the room/home’s humidity to this level and keep it that way throughout. Indeed, most humidifiers feature a humidistat that continuously tracks humidity levels in the home and automatically adjusts the humidifier’s output rate to add only the amount of moisture necessary to keep the desired indoor humidity level. Nearly all modern humidifiers allow you to set the desired indoor humidity level.

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Factors to Determine the Number of Humidifiers Necessary for the Home

Now that you understand how humidifiers work and their purpose, it’s easy to determine the number of units needed for your home. Consider the following;

1. Size of the home

The first thing you need to consider is the size of your home. Why? Because as we’ve seen, humidification is about raising the entire space’s (in this case, home) humidity level. The larger the home, the more moisture you need to add to attain the desired setting.

Fortunately, calculating the size of your home is a straightforward process. You can quickly check with the builder or your building plan (most owners have one) to determine the house’s size. Alternatively, determine the area of each room in the home (by multiplying length x width). Then add the areas of all the rooms.

In the end, you may only need one humidifier for a small home or multiple humidifiers when dealing with a large home.

2. Relative humidity (RH) in the home

Once you know your home’s size, the next step is to determine the relative humidity in your indoors. In simple terms, relative humidity is the amount of water in the air, expressed as a percentage of the maximum moisture that the air could hold at that given temperature. It’s the ratio of actual water vapor in the air to the saturation water vapor pressure.

As we’ve already seen, the ideal relative humidity in the home is 30-50%. Therefore, determining the relative humidity in the home (without the humidifier(s)) will tell you how much moisture you need to add to the home to raise moisture levels to the desired level.

Typically, you may need more humidifiers if the gap between the relative humidity (without humidifiers) and the desired humidity level is very large.

3. Humidifier type (console or room?)

There are three main types of humidifiers with regards to size – room, console, and furnace humidifiers. Room humidifiers are designed to serve only one room. Many can comfortably serve rooms up to 600 square feet. This means that you’d need multiple units for the entire home. Typically, you need one for every room, which often means up to eight or more units. Most room humidifiers are ultrasonic, though evaporative models are also common.

Console humidifiers are much larger. Most humidifiers in this category can comfortably serve up to 2,500 square feet – some even more. Therefore, you may only need one for the entire home. At most, you’d need two or three. Most console humidifiers are evaporative or steam-powered.

Finally, furnace humidifiers are the largest humidifier type. They are permanently installed to the heating furnace, thus effortlessly serve the entire home. You only need one furnace humidifier. All furnace humidifiers are evaporative or steam-operated.

4. Humidifier size (tank capacity)

Don’t confuse the tank size with humidifier type. Two room humidifiers, for instance, can have totally different sizes. The same applies to console and furnace humidifiers.

Among room humidifiers, for example, tank sizes range from 0.5 to four liters. A small-tank humidifier cannot serve a very large room. 0.5-liter units, for instance, are best used as personal humidifiers or in very small rooms, up to 150 square feet. You’d need several of these to serve just one room and dozens for the entire home.

The larger-sized tanks are a much better option when looking to humidity the entire home. For example, if you’re only interested in-room humidifiers, a 4-liter model should be enough for each medium-sized room (400-600 square feet), meaning that you only need one for each room. But, you can further reduce the number by going for console models with even larger tanks (up to 15+ liters) or furnace tanks that draw water directly from the home’s supply lines.

5. Humidifier’s output rate 

Finally, many people overlook the moisture output rate, but it’s just as important as the rest of the factors on this list. The output rate is the amount of moisture the humidifier can produce per given period. Usually, it’s given as gallons per hour or day (24 hours).

To understand why this metric is important, go back to the relative humidity factor we discussed earlier. You need to add a certain amount of moisture to your home at a steady rate to raise and maintain the indoor humidity levels at the desired setting. This means that you need a humidifier (or collection of humidifiers) that can constantly put out a certain amount (in gallons) of moisture.

Simply put – assuming a constant relative humidity and humidistat setting, a 4 gallons/day output humidifier can serve a larger area than a 2 gallon/day humidifier.


As you can see from the discussion, you may need one, two, or more humidifiers for your home, depending on several factors, including the house’s size, humidifier’s tank capacity, and the humidifier type. But even more importantly, always consider the relative humidity (RH) in the home and the humidifier’s output rate.

If you have enjoyed our article, check out our site for the best humidifier for 1000 square feet review and many more!


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Melanie Mavery is an aspiring HVAC technician who is fascinated by the trends and opportunities in the HVAC industry. She spends most of her day writing content on home improvement topics and outreaching to prospects.  She's always looking for ways to support HVACs!