Whole-House Humidifiers: Bypass vs. Power

Posted by HVACPartsShop.com on Aug 22nd 2017

Bypass vs Power humiderIn an earlier blog post we explained that the best way to fight dry air is to install a whole-house humidifier. We also mentioned two different types of whole-house humidifiers – the bypass humidifier and the power humidifier. So which should you install? Let’s get into the nitty gritty of which is right for you.

Both the bypass humidifier and the power humidifier have the same task at hand – to add moisture into the air of your home. Both do that by working in conjunction with your furnace or air handler, but there are some major differences in how they deliver the humidity to the rooms of your house.

The bypass humidifier is connected to the return of your furnace or air handler. It does not have a motor of its own and instead relies on the blower motor of the furnace to push warm air through it. The warm air is then pushed through the water panel that is within the humidifier and absorbs moisture from it. That moisture is then delivered back into the air stream and back into your home.

The bypass humidifier is probably the more common of the two, but the power humidifier is quickly gaining popularity and is replacing many bypass humidifiers in many of our customers’ homes.

When comparing the power humidifier to the bypass humidifier, the major differences are that it has its own blower motor and does not rely on the furnace blower motor. The fan delivers moisture to the supply, which sits above the heat source. Once humidity is created it is sent through the ductwork to the rest of the house and does not have to recirculate through the furnace and heat exchanger, as is the case with the bypass humidifier.

Let’s look at some of the pros and cons of each.

Bypass Humidifiers


A bypass humidifier is more affordable, it adapts to various water types (i.e. hard, soft) and requires very little maintenance.


It has to be connected to a bypass duct, which is aesthetically unpleasing and unfortunately can eat up more space. Also, since it uses the blower motor of the furnace the humidity that it creates has to be redistributed back through the furnace and heat exchanger again and again in a continuous loop. Therefore, a notable amount of moisture and humidity is lost. In other words, it is less efficient than the power humidifier.

Power Humidifiers


The power humidifier produces more humidity than the bypass humidifier. In fact it creates about one gallon of humidity more per day than the bypass humidifier. Another pro is that it can humidify more square feet and is ideal for larger homes.


The one downside to a power humidifier is that it is much more expensive to repair than the bypass humidifier.

We hope that this information is helpful in choosing the right whole-home humidifier for you and your home. And if you have any further questions please feel free to contact us. HVAC Parts Shop is here to help!