Is a dehumidifier cheaper than air conditioning for a damp room?

Yes for humidity alone, but it adds heat to the room, so in summer it can raise your cooling bill.

At the default usage on each page, central air conditioner costs about 4.7× as much to run as dehumidifier — $1,125 against $241 a year.

Why dehumidifier wins, and when it does not

• A dehumidifier draws about 500 W against central air's 3,500 W, so for a damp basement it is far cheaper.
• It releases the heat it removes back into the room. In a space you are also cooling, that heat is a cost you pay twice.
• In an unconditioned basement, where the extra heat does not matter, a dehumidifier is clearly the right tool.

What the difference is worth where you live

The 4.7× above holds at any price: both a dehumidifier and a central air conditioner scale with whatever you pay per kilowatt-hour. The money does not. Choosing dehumidifier over central air conditioner saves about $884 a year at the U.S. average, and $2,540 a year in Hawaii at 52.72¢ — against $632 in Nevada, the cheapest jurisdiction in the country. Swapping central air conditioner for dehumidifier is worth 4.0× as much in Hawaii as in Nevada, so what you pay per kilowatt-hour decides this more than the wattage on either label.

Both figures use each appliance’s typical wattage and default usage at the U.S. average of 18.34¢ per kilowatt-hour, and exclude fixed charges, taxes and time-of-use rates. Change the wattage, usage or state on either appliance’s own page to compare them on your terms, or read how to check a running-cost figure before trusting any of them.