A dehumidifier can reduce the load on your AC, but it won't cool your home

A dehumidifier removes moisture from the air; your air conditioner removes both heat and moisture. If your AC is already running, adding a dehumidifier will not make your home cooler — it will only make your AC work less hard to handle humidity. That matters only if your AC is struggling to keep up with moisture while the temperature is already where you want it, or if you live somewhere humid enough that your AC cools the air but leaves it feeling damp.

In most cases, a working AC does the job of dehumidifying on its own. A dehumidifier becomes useful only when your AC cannot keep the humidity low enough — usually because the AC is sized too small for the space, the home is very humid, or the AC runs in short cycles and does not run long enough to pull moisture out of the air.

The real question is whether your humidity problem exists. If your home feels sticky even though the temperature is comfortable, a dehumidifier will help. If the temperature is the problem, a dehumidifier will not fix it.

Key Takeaways

  • An air conditioner removes humidity as part of cooling, so a dehumidifier will not lower your temperature or reduce your cooling costs in most homes.
  • A dehumidifier helps only if your AC cools the air to the right temperature but leaves it feeling damp or sticky.
  • If your AC cannot keep humidity below 50 to 55 percent even when running constantly, adding a dehumidifier may help, but the real problem is usually an undersized AC unit.
  • Running a dehumidifier uses extra electricity and generates heat, which can actually make your AC work harder in small, sealed spaces.
  • Before buying a dehumidifier, check your current humidity level with an inexpensive meter to confirm the problem exists.

How your AC already removes humidity

Your air conditioner cools air by running it over cold coils. Moisture in the air condenses on those coils the same way water beads on a cold window, and that water drains out of your home through a condensate line. This happens automatically whenever your AC runs — you do not have to do anything.

The longer your AC runs, the more moisture it pulls out. If your AC is sized correctly for your home and your thermostat is set to a normal temperature, the humidity will drop to 40 to 50 percent on its own. You will not feel sticky, and you will not need a dehumidifier.

Problems start when your AC cannot run long enough or hard enough to handle the moisture load. This happens in humid climates, in homes where the AC unit is too small, or in homes with poor insulation or air sealing that let humid outside air leak in constantly.

When a dehumidifier actually helps

A dehumidifier helps when your home temperature is comfortable but the air feels damp. This usually means your AC is cooling the air to the right temperature but is not running long enough to pull out all the moisture. It can happen on mild days when the AC runs in short bursts, or in very humid climates where the moisture load is straightforward high.

Check your humidity with an inexpensive hygrometer (a humidity meter that costs $10 to $20). If your home stays above 55 percent humidity even when your AC is running, a dehumidifier can bring it down to a more comfortable 40 to 50 percent. Below 30 percent is too dry and can cause static, dry skin, and wood damage.

A dehumidifier works best in smaller rooms or closed spaces where the moisture is concentrated. Running one in a single bedroom or basement is more effective than running one in an open-plan home, because the unit can focus on a smaller volume of air.

The cost of running a dehumidifier alongside your AC

A dehumidifier uses 300 to 700 watts of electricity, depending on the size and model. Running one constantly costs roughly $15 to $40 per month in electricity, depending on your local rates. That is money your AC would not cost if the humidity problem did not exist.

A dehumidifier also generates heat as it runs. In a small, sealed space, that heat can make your AC work harder to cool the room back down, partly offsetting the benefit of removing moisture. In a large, open home, the heat is negligible. In a basement or bedroom with the door closed, it can be noticeable.

Before you buy, calculate whether the cost of running a dehumidifier is worth the comfort gain. If your humidity is only slightly high and the discomfort is mild, the electricity cost may outweigh the benefit.

Why a dehumidifier is not a substitute for a properly sized AC

If your AC cannot keep your home cool enough, a dehumidifier will not fix it. A dehumidifier removes moisture but does not cool air — it may even make the room slightly warmer because of the heat it generates. If your home is too warm, you need a larger AC unit, better insulation, or better air sealing to stop outside heat from leaking in.

Many people buy a dehumidifier hoping it will reduce their AC load and lower their cooling bills. It will not. If anything, running both at once uses more electricity than running the AC alone. The only way to lower cooling costs is to reduce the heat load on your home through insulation, window treatments, or a larger AC unit.

If your AC is running constantly and your home is still too warm and too humid, the unit is undersized. Adding a dehumidifier will not solve the problem — you will need to replace the AC with a larger one.

How to know if you need a dehumidifier

Start by measuring your humidity. Buy a hygrometer and check the reading in the main living areas of your home when your AC is running normally. If the humidity is consistently above 55 percent, a dehumidifier may help. If it is below 50 percent, your AC is already doing the job and a dehumidifier is unnecessary.

Next, check whether the problem is temperature or humidity. If your home feels too warm, the problem is cooling capacity, not humidity. If the temperature is comfortable but the air feels sticky or damp, humidity is the problem. Only in the second case will a dehumidifier help.

Finally, consider the location. If the humidity problem is limited to one room or basement, a portable dehumidifier in that space will work better than trying to dehumidify the whole home. If humidity is high throughout the house, the problem is likely your AC unit or your home's air sealing, and a dehumidifier is a temporary patch, not a solution.

Dehumidifier types and what they cost

Portable dehumidifiers range from $100 to $400 and work in single rooms or small spaces. They pull moisture into a tank that you empty by hand, or they drain continuously into a floor drain or window. Smaller units (30 to 50 pints per day) cost less but work slowly in humid climates. Larger units (70 to 100 pints per day) cost more but handle high humidity faster.

Whole-home dehumidifiers are built into your HVAC system and cost $1,500 to $2,500 installed. They work alongside your AC and drain automatically. They are worth the cost only if your humidity problem is severe and affects the whole house, and only if your AC unit is already the right size for cooling.

Before buying any dehumidifier, rent one for a week or two if possible. This lets you test whether removing humidity actually solves your comfort problem without spending money on a unit you might not need.

Frequently Asked Questions

Will a dehumidifier lower my AC bills?

No. A dehumidifier uses extra electricity and generates heat, which can make your AC work harder. Running both together costs more than running your AC alone. The only way to lower cooling bills is to reduce heat entering your home through better insulation, window coverings, or air sealing.

Can I use a dehumidifier instead of running my AC?

No. A dehumidifier removes moisture but does not cool air. If your home is too warm, you need air conditioning. A dehumidifier can only supplement an AC that is already cooling your home to the right temperature.

What humidity level should I aim for?

Aim for 40 to 50 percent humidity. Below 30 percent causes dry skin, static, and wood damage. Above 55 percent feels sticky and can promote mold and dust mites. Your AC should reach this range on its own if it is sized correctly and running normally.

Does a dehumidifier work in a humid climate?

A dehumidifier works in humid climates, but it works slowly and costs more to run because the moisture load is constant. In very humid areas, a whole-home dehumidifier built into your HVAC system is more effective than a portable unit, though it is also more expensive.

Should I run my dehumidifier all the time?

Run it only when your humidity is above 55 percent. Check with a hygrometer before turning it on. Running it constantly wastes electricity and can make your home too dry, which causes discomfort and damage to wood and furniture.