Whole House vs Portable Dehumidifiers
When faced with the sticker shock of a whole house dehumidifier, many people wonder how they are different from a small portable dehumidifier that costs less than $200 and can be found at Wal-Mart or Home Depot. What are the differences between a $200 dehumidifier and a $1000 dehumidifier?
Capacity (Water Removal)
The main difference between a true whole house dehumdifier and a small portable dehumidifier is capacity. A larger compressor and condensing coils allow whole house dehumidifiers to remove more moisture from the air in less time. Manufacturers of portable dehumidifiers typically inflate the performance and indicate their capacity based on 100% relative humidity (which is an environment that is nearly impossible to find). Under these conditions moisture is readily available and easily removed, making it easy to inflate the performance of a dehumidifier. In a much more realistic environment the performance of portable dehumidifiers is significantly lower.
The following illustrates the capacities of portable and whole house dehumidifiers.
Whole House Dehumidifiers
Whole house dehumidifers are typically rated for performance at AHAM, which indicates how much moisture can be removed from an 80° F space with 60% relative humidity. Every whole house dehumidifier is rated this way so you can easily compare how units will perform under the same conditions. When a whole house dehumidifier is rated to extract 100 pints per day, you can expect that it will be able to come pretty close to that capacity in a typical basement or crawlspace.
When we say "small portable dehumidifers" we're talking about the plastic models that are typically knee-high and usually have a bucket to collect the moisture. Portable dehumidifiers are meant to be moved from room to room where humidity is a problem, but are generally too small in both size and capacity to adequately dehumidify your entire home.
A whole house dehumidifier is typically much larger and is usually made from stainless steel or heavy-duty molded plastic. Whole house dehumidifiers may be portable in the sense that they are on casters and can be moved easily, but you would not want to try and pick one up and move it from room to room. They come in various shapes and sizes and may have large ducts where moist air can enter and exit.
CFM (Air Movement)
Most portable dehumidifiers do not disclose a CFM rating, which is a very important part of the dehumidification equation. All dehumidifiers must move air across the internal components in order to extract moisture. The CFM rating indicates how many cubic feet of air per minute is pulled across the condensing coils of the dehumidifier. Smaller dehumidifiers with low CFM ratings will not be able to cycle enough air through the unit to adequately affect the humidity levels in larger areas. This is the reason why most portable dehumidifiers are meant to be used in a single room only.
Whole house dehumidifiers, on the other hand, are typically equipped with large fans that can move a lot of air across the condensing coils (which is where the magic happens). Additionally, most whole house dehumidifiers can be equipped with ducting to make the most efficient use of the fan. Consequently, whole house dehumidifiers tend to be a little louder than portable dehumidifiers (but not always). Some whole house dehumidifiers offer optional muffler kits to reduce the noise output if it becomes problematic.
Operating Temperature Range
As the ambient temperature drops, moisture becomes much more difficult to extract from the air. Many whole house dehumidifiers are designed to operate in parts of your house that may not be heated such as crawlspaces or unfinished basements. As the ambient air temperature drops, a high quality whole house dehumidifier will do a better job of maintaining capacity.
Most portable dehumidifiers lack the muscle to remove moisture in lower temperature environments. As the air in your basement drops to a temperature of 60°F temperature (not uncommon for a basement), a small portable dehumidifier will not be very effective. Even though the temperature in the main living areas of your home might be 70 - 80°F, your basement or crawlspace is usually much cooler. In these conditions a portable dehumidifier will run constantly and not extract enough moisture to make much of a difference.
Many consumers fail to consider how shipping will impact the dehumidifier. Small portable dehumidifiers are typically made of plastic, and often the heavy internal components (such as the compressor and fan motor) can break free from the plastic housing and bounce around during shipping. Good retailers will replace the damaged unit, but that is an inconvenience and there is no guarantee that internal damage won't show up until after you've owned the dehumidifier for a length of time.
Another shipping issue specifically with dehumidifiers has to do with the orientation of the compressor. Compressors should be stored in the proper orientation or you might have lubrication problems (compressors rely on gravity to keep the moving parts lubricated). Since most portable dehumidifiers ship via standard parcel carrier, it is unlikely that the unit will be shipped in the correct position.
In the past we offered these types of portable plastic dehumidifiers, but discontinued their sale because of the large number of them that were damaged during shipping. Parcel carrier service (like UPS, FedEx and DHL ground) was simply too rough for that type of product. Despite additional packaging measures on our part, nearly 40% of all portable dehumidifier shipments ended up damaged.
Whole house dehumidifiers, on the other hand, are almost always shipped on a pallet by a freight carrier such as FedEx Freight. Whole house dehumidifiers are far less likely to be damaged internally during shipping because there is usually a solid metal frame on the inside that all the components are bolted to. Occasionally we see some slight damage to the outside of the unit (a dent in a metal panel, for example), but 99% of the time the unit operates just fine upon delivery.
Portable dehumidifiers are typically so inexpensive that replacement parts are not available (and the plastic cases are not meant to be disassembled and repaired). Since portable dehumidifiers will tend to run quite a bit more than whole house dehumidifiers, you can expect some service issues after a few years of use. In truth, most portable dehumidifiers are intended to run for a while, and then be discarded and replaced with a new one.
Whole house dehumidifiers, on the other hand, offer complete replacement part lists and are fairly easy to take apart and repair.
The Bottom Line
If you're looking for a single-room dehumidifier solution, then a small portable dehumidifier should work just fine. If you need to solve humidity problems in a large area (like a basement or crawlspace), then you should really be looking at a true whole-house unit.
Many homeowners we talk to are looking for larger whole-house dehumidifiers after having tried various portable dehumidifiers in the past. In most cases the portable units that these people are buying are far too small in actual capacity to tackle humidity issues in larger areas.
Although a whole-house dehumidifier requires a greater initial investment, they'll run less often and consume less energy in the long-run. If you're looking to solve or prevent humidity problems in your home, the money you spend on a whole-house dehumidifier will pale in comparison to the cost of repairing moisture-related problems down the road.
If you're still not sure whether a whole house dehumidifier is right for you, then you should check out our article on Misconceptions About Whole House Dehumidifiers.