Aprilaire 700 Power Humidifier - 18 GPD with Automatic Digital Humidistat

Are you suffering from dryness in your home? Tired of touching anything metal in fear of being shocked by static electricity? The Aprilaire 700 power humidifier is just what you need, covering up to 4,200 square feet!

Since 1954, when Aprilaire introduced the first whole-home humidifier,  they have been the industry leader in ducted whole house humidification.  The Aprilaire 700 power humidifier has led the charge in home comfort. 


With an 18 gallon per day output, the Aprilaire 700 can humidify a home up to 4,200 square feet.  This unit mounts directly to the duct of your heating and cooling system, allowing the humidity to be placed into the airflow and distributed evenly throughout the home. The 700 humidifier hooks up to a water line so you do not need to worry about filling it multiple times a day. With a built in fan the humidifier pulls warm air directly from the furnace, increasing its effectiveness.


Benefits of Evaporative Humidification

  • Prevents Flu and Allergies
  • Neutralizes Static Electricity
  • Reduces Pet Dander and Discomfort
  • Protects Fine Furniture and Wood Floors
  • Relieves Dry Skin & Scratchy Throats
  • Reduces Heating Costs


The 60 automatic controller that comes standard with the Aprilaire 700 humidifier mounts directly to the ductwork of your heating and cooling system to accurately read and deliver the appropriate amount of humidity.  Equipped with notification lights, you are alerted if your humidifier is not working properly (red), needs a new #35 water panel (yellow), or is working properly (green). Sensing the outdoor temperature and the indoor humidity level, the automatic humidistat will call for the ideal amount of indoor humidification to ensure you and your family are as comfortable as possible.

The 700 humidifier by Aprilaire requires a plenum opening of 14 3/4" by 14 5/16".  For electrical reference, this unit operates on 120 Volts at 60Hz with a .8 AMP requirement.  Due to the nature of evaporative humidification this unit can be installed on either the supply or return duct of the heating and cooling system. If the Aprilaire humidifier is being installed on a heat pump system it is best to hook the unit up to a hot water line.


Using a genuine Aprilaire #35 water panel is highly suggested.  This water panel was designed specifically for the Aprilaire 700 humidifier and provides the most comfortable and efficient output. Don't trust the aftermarket products to provide the same quality and overall experience as the genuine #35 water panel.


Aprilaire recommends a #4750 maintenance kit be used each humidification season to ensure that your 700 humidifier is operating optimally.


How to Videos


Changing The Water Panel
Seasonal Maintenance
Aprilaire 700 Fan Powered Humidifier Overview
Aprilaire 700 Fan Powered Humidifier Water Panel Change
Aprilaire 700 Fan Powered Humidifier Maintenance


If you have any questions regarding this product, please use the HVAC.com Contractor Directory to connect with a trusted contractor in your area.

  • Brand: Aprilaire
  • Genuine OEM Product: Yes
  • Type: Power Humidifier
  • Control Type: Automatic
  • Coverage: Up to 4,200 sq. ft.
  • Water Panel: Aprilaire #35
  • Evaporative Rate: .75 Gallons Per Hour
  • Electrical: 24V
  • Product Measurements: 15.9" W x 18" H x 10.34" D
  • Plenum Opening: 14.75" W x 14.31" H
  • Includes: 24V VAC Transformer, Automatic Digital Humidistat, Remote Temperature Sensor, Saddle Valve, 1 Aprilaire #35 Water Panel
  • This product comes with a 5 year limited manufacturer's warranty from the date of installation.
    Reviews Write a Review
    • KCG67

      Arrived in 2 days, moderate install and is better than expected!!

    • JoeD

      Delivery was super quick. So HVAC.com is on spot. YOU MUST LOOK FOR the small manual that is with the valve packaging YOU NEED THIS unless you are a pro. Crazy amount of connections. The hole you cut with the template will make the bottom two screw holes (to attach to your furnace) un-usable. The included valve is JUNK! Ditch it and put in a real valve. So far its good. No noise, increased moisture, etc.

    • Bolt

      I installed this myself - home do-it-yourselfer. Fairly easy install, if you read and follow directions carefully. I was able to utilize the outdoor probe and my house has held steady at 40% humidity ever since. I have an independent humidity sensor on the main floor, which is always in agreement (within 1%) of the digital thermostat mounted on the return.

    • KPN3

      Very quick shipping & the humidifier works fantastic. I will definitely buy from them again.

    • Bob17

      Super fast and efficient shipping. Product arrived in perfect condition.

    • GoldenGirl61

      I bought this for my husband and it has made a big difference in our house. The installation only took my son-in-law a few hours to install!

    • Kris R

      I purchased this unit from HVAC.com and had it installed by my HVAC guy. I was present while the install took place and it appeared to be pretty straight forward. It was installed on the return side because of clearance issues on the supply. It was set once and has run flawlessly since. In the two months since it has been installed the outside temps have been from the 60's to the low 20's. The external temp sensor automatically adjusts the unit to keep the house between 35% - 40% RH. I am very pleased with the product and the ease of use. Purchasing from HVAC.com was simple and I wouldn't hesitate to purchase from them again.

    • FastEddie

      The Aprilaire 700 was a replacement so installation was a breeze and doing it myself saved a bundle of money. Works great.

    • PP Jr

      I am totally satisfied with this product. Works better than other brands it replaced. Get the digital system. Highly recommend it and buying it from Humidifiers.com. They were prompt in handling my order and getting it to me.

    • Steven

      I purchased the Aprilaire 700 from Humidifier.com over the holidays. There was a little delay in processing my order, but it was very understandable since it was the holidays. One processed I got got my order quickly. The price was great and the shipping was quick! I installed the Aprilaire 700 myself to my Rudd 80% furnace. I hooked the Aprilaire to a hot water line and mounted it on the supply duct. I didn't use the supplied digital control, instead I hooked the humidifier up to my 2nd generation Nest thermostat. I have no experience with HVAC but was able to do everything myself in about 6 hours of work including trips to the store etc. Be aware that if you don't have a humidifier installed you will be to buy some items as stated in the instructions. It cost me about $125 in parts to install, but I had to buy some extra things like a relay and new thermostat wire because of my Nest Setup. After 12 hours of use my house went from 12% humidity to 35% humidity. It's working well with or without the furnace being on. I can already notice a change and it's a very nice luxury to have. I highly recommend this item so far and humidifiers.com. I also recommend installing yourself if you are handy.

    • Darren

      I have my unit set to the #4 setting and within 2 days my house went from 18% to 35% rh. I have an older house with a lot of natural oak so I was relieved when the humidity came up so quickly. If you are planning to install it yourself you will need some extra supplies like tin shears, 1/2" drain hose, and thermostat wiring. There is quite a lot to wire up since this unit works in unison with your furnace blower. However, once the unit is installed it is completely automatic. One feature that I really liked was that because it has its own fan, the warm air from your furnace is simply circulated through the unit and back into the duct. This eliminates the intake port that most similar units have. The only negative thing I can say is that the unit is not completely powered by the 120v plugin. You must install a 24v transformer (included with the humidifier) and wire up a separate circuit to operate the solenoid valve that turns the water on to the unit.

    • Ted

      After dealing with 3 small in-room humidifiers I decided to take the plunge to a whole house. It wasn't an easy install because of my down-flow furnace duct work arrangement, but once I figured that out it was easy. It arrived quickly and took me 6 hours to install, plumb, and wire. Works great so far. Love the automatic features. Set it and forget it!

    • B

      Well, after about two years of stalling on buying a whole home humidifier, I finally decided on the Aprilaire 700. After checking some online retailers, I was extremely glad to find the absolute best deal on the humidifier here and the best pricing on shipping. Also I ordered this on a weekend, and got the product the next Wednesday. Thank you Humidifiers.com for excellent pricing and service! B

    • Marilyn

      We are very satisfied with our dealings with Humidifiers.com. Delivery was made in a good time span. Thank you.

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    Aprilaire 700 Power Humidifier - 18 GPD with Automatic Digital Humidistat