--- product_id: 1149294 title: "AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White" brand: "aprilaire" price: "$897.24" currency: USD in_stock: true reviews_count: 13 category: "Aprilaire" url: https://www.desertcart.us/products/1149294-aprilaire-400-whole-house-humidifier-automatic-water-saver-furnace-humidifier store_origin: US region: United States of America --- # Covers up to 5,000 sq.ft. 17 gallons/day water capacity Dual sensors for auto humidity control AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White **Brand:** aprilaire **Price:** $897.24 **Availability:** βœ… In Stock ## Summary > πŸ’§ Elevate your home's air game with smart, sustainable whole-house humidity! ## Quick Answers - **What is this?** AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White by aprilaire - **How much does it cost?** $897.24 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.us](https://www.desertcart.us/products/1149294-aprilaire-400-whole-house-humidifier-automatic-water-saver-furnace-humidifier) ## Best For - aprilaire enthusiasts ## Why This Product - Trusted aprilaire brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - β€’ **Eco-Friendly Water Saver:** Innovative design evaporates 100% of water used, cutting waste and lowering your utility footprint. - β€’ **Health-Boosting Humidity:** Maintains optimal 40-60% humidity to reduce allergens, viruses, and protect your home’s valuables. - β€’ **Whole-Home Comfort Mastery:** Effortlessly humidifies up to 5,000 sq.ft. for consistent, cozy air throughout your space. - β€’ **Smart Auto-Humidity Control:** Dual sensors monitor outdoor temp & indoor humidity, delivering perfect moisture 24/7β€”set it and forget it. - β€’ **Seamless Integration & Quiet Operation:** Includes digital control, outdoor sensor, and auto shut-off for hassle-free, whisper-quiet performance. ## Overview The AprilAire 400 Whole-House Humidifier is a U.S.-made, evaporative system designed for homes up to 5,000 sq.ft. It features a 17-gallon daily capacity and dual sensors that automatically adjust humidity based on indoor and outdoor conditions. Its water-saving technology ensures 100% evaporation of water used, promoting eco-efficiency. With digital controls, quiet operation, and health-focused humidity levels, it enhances indoor air quality while protecting your home and wellbeing. ## Description AprilAire introduced the first evaporative humidifier for forced air furnace systems back in 1954. Since that time, AprilAire continues to lead the industry in whole home humidification systems. Our evaporative humidifiers work by piping water into the distribution tray located at the top of the humidifier. The water is uniformly distributed across the width of the tray and through a scientifically designed system of outlets. It flows by gravity over the Water Panel evaporator. Dry, hot air from the HVAC system is moved through the moisture-laden Water Panel evaporator. Natural evaporation takes place, the water is turned to vapor, and the humidified air is circulated throughout your home. This unit is uniquely designed to evaporate 100% of the water going into the humidifier. It incorporates a special two-stage float system to maintain the optimal amount of water and protect against overflow. In the unlikely event the float system fails, it is recommended an overflow tube (1/2 inch inside diameter) be installed to the base of the humidifier and run to a condensate pump, a sink, or a floor drain. Follow the required maintenance instructions. INCLUDED IN THE BOX: Installation instructions and template, humidifier with built-in bypass damper, 24 VAC transformer, automatic digital humidifier control with sensor, outdoor temperature sensor, saddle valve, solenoid valve, and Model # 45 Water Panel Review: Works great - I spent a lot of time deciding on a humidifier. I checked humidity levels all over the house and they were pretty consistent at 23-25% at 25-30 degrees outside. My home is 3000 sf and the specs for this model put that size at its limit. I was debating between the 600 and this model, the 400. Ultimately, I picked this model for its efficient water usage and after a lot of use I am positive I made the right choice. Unlike other humidifiers this one does not drain water unless there is a problem. Water still comes in from the top and flows over the water panel but water flow stops when a holding cup gets filled on the bottom. Other models just keep running water until there is no longer a call for humidity by the humidistat. The water in the cup is then wicked up and then water flow turns on again, This happens over and over as needed. Installation was pretty straight forward. It took $36 worth of parts at the hardware store and about 3 hours to get it installed. Tape the supplied outline on either the supply (make sure it's above the AC Coil) or the return duct and cut a hole. Find a spot for the bypass (a 6" round duct) on the other duct and make a hole there. The unit mounts the the duct with several screws (self taping sheet metal screws make fast work) and two screws for the 6" duct coming off of it. Just a tip - if the unit can be mounted with the first section of duct attached then screw it on before mounting it. I had a little trouble getting a drill in there once it was mounted to the furnace. I used metal tape on the edges of the unit itself and all the duct joints. I used two adjustable elbows and a short section of flex duct to make the connection between the unit and the bypass. Now for the water. I did more research on this than I care to admit. Here's what I kept reading, if the furnace does not have long run cycles then run hot water to the humidifier. They explained it that if the furnace doesn't get hot for a long time then the humidifier will not work as efficient. So, with that logic I ran hot water to it. The kit includes a saddle valve which makes for an easy install. Unfortunately these aren't the greatest so I put in a different valve. This took more time than anything else. Once the valve was in, I ran the shortest possible length of tubing to the humidifier in an attempt to keep the incoming hot water as hot as possible. After running the humidifier for some time now, my opinion is the hot water makes no difference. The water flow doesn't run enough to keep it hot for very long. I found that water will run for maybe 1 minute max before the fill cup fills and shuts off the water. After a couple minutes the cup will empty and water will run again, but this time for even less time because the water panel is already wet. The heat from the furnace, even on a short run time, seems to do just fine. Next was the wiring. Turn off power to the furnace to avoid frying the board. I tapped into an existing 24VAC line for the power, connected the C (common) and H (humidifier) from the furnace board, the white and yellow from the humidifier and the outside temp sensor wires to the humidistat. I mounted the humidistat before the humidifier on the cold air return. The humidistat will work in automatic mode based on outside temperature. I found this a little conservative for my home. When in manual mode I can maintain over 40% humidity without a problem. I usually don't keep it this high but wanted to see if it could do it. I took the same humidity readings as prior and have a reading within 3% throughout the house. Review: Very effective - Let me start off by saying I installed this myself, and I am a technician by profession, so it may have been easier for me than for some people. It did not seem very complicated to me though, and the directions included appear very clear and straightforward. I think anyone with some basic tools and mechanically inclined could do this themselves, otherwise you might want to hire a professional installer. The kit included everything I needed except sheet metal screws and tubing (1/4" copper for water supply, 1/2 clear vinyl for drain), and some additional 14-20 AWG wire nuts. I also bought an additional T-fitting with 1/4 turn shut off valve to hook up the water supply in my 1/2" copper hot water pipe. I don't recommend using the saddle valve they provide in the kit for the piping, as they frequently fail, and do not meet code. I mounted the unit on the return manifold, and used a couple of 90Β° 6" elbows and a few feet of flexible HVAC hose for the bypass duct, and sealed it all with the silver foil HVAC tape. As for the functionality of the unit, it's working great so far. I really like the water saving feature on it. It comes with a composite material filter (paper/metal screen) and a tray with float sensors to shut off the water valve if it gets full. This makes for a much more economical use of water in my opinion, and still has an overflow drain tube in case of malfunction. I like the outdoor temperature sensor to use the automatic feature for humidity adjustment, and it also has a feature to turn on the furnace blower to circulate and humidify the air if the humidity level is too low, separate from the thermostat control, which is very nice. Both features work perfectly so far, and my relative humidity went up 10% after the first day. This is the most precise and full control featured humidifier I saw at this price point, and was a very good value for the money. ## Features - BUY WITH CONFIDENCE This humidifier was designed and manufactured in the U.S.A. by AprilAire – the inventor of the whole home evaporative humidifier, and the leader in indoor air quality solutions - FULL COVERAGE up to 5,000 square feet in tightly built homes with a capacity of 17 gallons per day - AUTOMATIC HUMIDIFIER with dual sensors to monitor and respond to both outdoor temperature and indoor relative humidity to deliver optimum humidity 24/7 throughout the home – simply set it and forget it - CONSERVES WATER using a unique process that evaporates 100% of the water flowing into the water panel - HUMIDITY FOR HEALTH AprilAire Humidifiers can help you maintain optimal humidity in your home of 40% – 60% which has been shown to reduce the incidence of respiratory infections and symptoms related to allergies and asthma by minimizing the formation of bacteria and viruses, fungi, and dust mites. In addition, you’ll feel more comfortable while also preserving items in your home susceptible to damage from changing humidity or dry conditions ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B004PDDZRS | | Best Sellers Rank | #1,640,405 in Home & Kitchen ( See Top 100 in Home & Kitchen ) #1,238 in Humidifiers | | Brand | Aprilaire | | Brand Name | Aprilaire | | Capacity | 17 gallons_per_day | | Color | Gray | | Control Method | App | | Customer Reviews | 4.4 out of 5 stars 317 Reviews | | Filter Type | Wicking Evaporative | | Floor Area | 4000 Square Feet | | Global Trade Identification Number | 00686720004001, 00686720104008 | | Included Components | 24VAC Transformer, Humidifier Control, Valves, Installation Instructions | | Item Dimensions D x W x H | 10.25"D x 15.38"W x 15.75"H | | Item Shape | Rectangular | | Item Type Name | Humidifiers Evaporative | | Item Weight | 8.8 Pounds | | Manufacturer | Research Products Corporation | | Material | Plastic | | Model Name | Humidifiers Evaporative | | Model Number | 400 | | Operation Mode | Evaporative | | Other Special Features of the Product | Adjustable Humidity Control, Auto Shut Off, Digital Display, Humidistat, Quiet, Service Filter Indicator | | Part Number | 400Z | | Power Source | ac | | Room Type | Whole-House | | Runtime | 0 minute | | Special Feature | Adjustable Humidity Control, Auto Shut Off, Digital Display, Humidistat, Quiet, Service Filter Indicator Special Feature Adjustable Humidity Control, Auto Shut Off, Digital Display, Humidistat, Quiet, Service Filter Indicator See more | | UPC | 686720104008 | | Unit Count | 1.0 Count | | Voltage | 24 Volts (AC) | | Warranty Description | 5 Year Manufacturer | ## Product Details - **Brand:** Aprilaire - **Special Feature:** Adjustable Humidity Control, Auto Shut Off, Digital Display, Humidistat, Quiet, Service Filter Indicator - **Color:** Gray - **Floor Area:** 4000 Square Feet - **Operation Mode:** Evaporative ## Images ![AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White - Image 1](https://m.media-amazon.com/images/I/713QElbV4GL.jpg) ![AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White - Image 2](https://m.media-amazon.com/images/I/51sE1GWJhML.jpg) ![AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White - Image 3](https://m.media-amazon.com/images/I/71jYVlDaKFL.jpg) ![AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White - Image 4](https://m.media-amazon.com/images/I/71Z5g9di6sL.jpg) ![AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White - Image 5](https://m.media-amazon.com/images/I/71syfOrti0L.jpg) ## Available Options This product comes in different **Style** options. ## Customer Reviews ### ⭐⭐⭐⭐⭐ Works great *by B***N on February 8, 2014* I spent a lot of time deciding on a humidifier. I checked humidity levels all over the house and they were pretty consistent at 23-25% at 25-30 degrees outside. My home is 3000 sf and the specs for this model put that size at its limit. I was debating between the 600 and this model, the 400. Ultimately, I picked this model for its efficient water usage and after a lot of use I am positive I made the right choice. Unlike other humidifiers this one does not drain water unless there is a problem. Water still comes in from the top and flows over the water panel but water flow stops when a holding cup gets filled on the bottom. Other models just keep running water until there is no longer a call for humidity by the humidistat. The water in the cup is then wicked up and then water flow turns on again, This happens over and over as needed. Installation was pretty straight forward. It took $36 worth of parts at the hardware store and about 3 hours to get it installed. Tape the supplied outline on either the supply (make sure it's above the AC Coil) or the return duct and cut a hole. Find a spot for the bypass (a 6" round duct) on the other duct and make a hole there. The unit mounts the the duct with several screws (self taping sheet metal screws make fast work) and two screws for the 6" duct coming off of it. Just a tip - if the unit can be mounted with the first section of duct attached then screw it on before mounting it. I had a little trouble getting a drill in there once it was mounted to the furnace. I used metal tape on the edges of the unit itself and all the duct joints. I used two adjustable elbows and a short section of flex duct to make the connection between the unit and the bypass. Now for the water. I did more research on this than I care to admit. Here's what I kept reading, if the furnace does not have long run cycles then run hot water to the humidifier. They explained it that if the furnace doesn't get hot for a long time then the humidifier will not work as efficient. So, with that logic I ran hot water to it. The kit includes a saddle valve which makes for an easy install. Unfortunately these aren't the greatest so I put in a different valve. This took more time than anything else. Once the valve was in, I ran the shortest possible length of tubing to the humidifier in an attempt to keep the incoming hot water as hot as possible. After running the humidifier for some time now, my opinion is the hot water makes no difference. The water flow doesn't run enough to keep it hot for very long. I found that water will run for maybe 1 minute max before the fill cup fills and shuts off the water. After a couple minutes the cup will empty and water will run again, but this time for even less time because the water panel is already wet. The heat from the furnace, even on a short run time, seems to do just fine. Next was the wiring. Turn off power to the furnace to avoid frying the board. I tapped into an existing 24VAC line for the power, connected the C (common) and H (humidifier) from the furnace board, the white and yellow from the humidifier and the outside temp sensor wires to the humidistat. I mounted the humidistat before the humidifier on the cold air return. The humidistat will work in automatic mode based on outside temperature. I found this a little conservative for my home. When in manual mode I can maintain over 40% humidity without a problem. I usually don't keep it this high but wanted to see if it could do it. I took the same humidity readings as prior and have a reading within 3% throughout the house. ### ⭐⭐⭐⭐⭐ Very effective *by A***3 on December 15, 2019* Let me start off by saying I installed this myself, and I am a technician by profession, so it may have been easier for me than for some people. It did not seem very complicated to me though, and the directions included appear very clear and straightforward. I think anyone with some basic tools and mechanically inclined could do this themselves, otherwise you might want to hire a professional installer. The kit included everything I needed except sheet metal screws and tubing (1/4" copper for water supply, 1/2 clear vinyl for drain), and some additional 14-20 AWG wire nuts. I also bought an additional T-fitting with 1/4 turn shut off valve to hook up the water supply in my 1/2" copper hot water pipe. I don't recommend using the saddle valve they provide in the kit for the piping, as they frequently fail, and do not meet code. I mounted the unit on the return manifold, and used a couple of 90Β° 6" elbows and a few feet of flexible HVAC hose for the bypass duct, and sealed it all with the silver foil HVAC tape. As for the functionality of the unit, it's working great so far. I really like the water saving feature on it. It comes with a composite material filter (paper/metal screen) and a tray with float sensors to shut off the water valve if it gets full. This makes for a much more economical use of water in my opinion, and still has an overflow drain tube in case of malfunction. I like the outdoor temperature sensor to use the automatic feature for humidity adjustment, and it also has a feature to turn on the furnace blower to circulate and humidify the air if the humidity level is too low, separate from the thermostat control, which is very nice. Both features work perfectly so far, and my relative humidity went up 10% after the first day. This is the most precise and full control featured humidifier I saw at this price point, and was a very good value for the money. ### ⭐⭐⭐⭐ Excellent product with "OK" instructions *by A***N on January 21, 2026* I bought the AprilAire 400 specifically because my basement doesn't have a floor drain near the furnace. The best part about this unit is that it uses a float system to evaporate all the water, so it doesn't dump anything out of a drain line. It saved me the huge hassle and extra cost of having to buy and install a condensate pump. The installation went okay, but the instructions weren't the best. They get the job done, but they aren't the best or most clear. I had to Google a few things to make sure I had it all installed correctly. Overall, it’s a solid humidifier that actually works. If you're in a spot where you can't easily run a drain line, this is definitely the one to get. It’s kept my house much more comfortable this winter without any leaks or mess. This can be installed without the outdoor temperature sensor installed, you have to flip a switch in the controller to manual mode. I plan to install the sensor next summer as it's too cold outside to work on a project like that. Overall works great for my application and brought my indoor humidity from 5-10% up to 35% where I set it at. ## Frequently Bought Together - AprilAire 400 Whole-House Humidifier, Automatic Water Saver Furnace Humidifier, Large Capacity Whole-House Humidifier for Homes up to 5,000 Sq. Ft., White - AprilAire 5844 Humidifier Installation Kit for AprilAire Whole Home Humidifiers with Automatic Control, Compatible with AprilAire Humidifier Models: 400, 500, 600 Black --- ## Why Shop on Desertcart? - πŸ›’ **Trusted by 1.3+ Million Shoppers** β€” Serving international shoppers since 2016 - 🌍 **Shop Globally** β€” Access 737+ million products across 21 categories - πŸ’° **No Hidden Fees** β€” All customs, duties, and taxes included in the price - πŸ”„ **15-Day Free Returns** β€” Hassle-free returns (30 days for PRO members) - πŸ”’ **Secure Payments** β€” Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** β€” Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.us/products/1149294-aprilaire-400-whole-house-humidifier-automatic-water-saver-furnace-humidifier](https://www.desertcart.us/products/1149294-aprilaire-400-whole-house-humidifier-automatic-water-saver-furnace-humidifier) --- *Product available on Desertcart United States of America* *Store origin: US* *Last updated: 2026-07-25*