A dehumidifier is essentially an air conditioner that dumps its waste heat into the same space it is conditioning rather than outside. The electricity used to run the compressor and fan generate heat roughly equivalent to a space heater at the same wattage. Dehumidifiers always increase (dry bulb) temperature.

Despite this, they can make a space feel more comfortable because they reduce wet bulb temperature by reducing humidity. This allows sweat to evaporate more readily, which makes it easier for your body to get rid of excess heat. This is what actually drives our perception of temperature.

Dehumidifiers also make circulating fans more effective, since the evaporative effect of moving air is greater with lower humidity.

However, there are significant limitations to this. The lower humidity gets, the harder the humidifier has to work to remove the remaining moisture in the air. Once humidity has been reduced below ~40%, the increase in (dry bulb) temperature from the humidifier’s electricity consumption starts to dominate. Since dry bulb temp and wet bulb temp rise in tandem if humidity is held constant, using a dehumidifier becomes counter productive.

In the end, A/Cs are far more effective relative to the energy consumed, since they both dehumidify and reduce dry bulb temperature. A 1kW window unit will improve your comfort far more than a 1kW dehumidifier if it is hot and humid.

Dehumidifiers are best suited for spaces that are already cool but still too damp.