Less effective at cooling, more effective at dehumidifying (it seems there is a presumption that dehumidification is roughly linear with operating time.)
Both air conditioners and dehumidifiers are built on heat pumps. They both dehumidify in the same way: water condenses on a coil and drains away. But an AC unit pumps the extracted heat outside, and a dehumidifier pumps it back inside. When it's hot and humid, it wouldn't make sense to forgo the opportunity to pump heat outside.
A better solution is to get some variation of a two-stage air conditioner. Instead of a compressor that's either off or on, these have a compressor that can run at two speeds. Most of the time, it runs at the lower speed and behaves like an AC that is undersized, runs longer, and dehumidifies well. But when it gets really hot, it goes up to full speed so it can the temperature down. Compared to a single-stage AC, it costs more, but it's more energy-efficient and quieter and more comfortable because of smaller temperature swings.
These days they also variable-speed air conditioners that can adjust in tiny increments and run the compressor at almost any speed, so they are kind of the next generation beyond two-stage. They more or less run continuously, adjusting their power level instead of having an on/off duty cycle. It costs more than a two-stage, but it is even more efficient, quieter, and comfortable.
Most folks will need an AC unit regardless, and there is already a condensate drain line from the air handler. You could get an additional dehumidifier if your use case calls for it (dehumidification without a need to cool) but the cost is non-insignificant.
I have explored a dehumidifier for my Florida home, and after looking at the numbers, it just made more sense to tighten up the envelope and set the AC to 74. I have solar on the roof though, so the energy costs aren’t terribly high (vs possible mold remediation) for this approach. YMMV.
A dehumidifier is an air conditioner. It's the same device.
It operates a compressor that condenses a fluid with a boiling point below room temperature. As it condenses to a liquid, it generates a lot of heat. This heat is removed from the liquid. The liquid is then allowed to boil, which pulls heat from the environment.
In an air conditioner, the heat is radiated outside, and the cool air is vented inside. In a dehumidifier, the air is sucked in, blown over the cool radiator, which creates condensation which is collected, then blown over the hot radiator, and then blown back into the house.
So you might as well just use an AC and be more comfortable. There aren't any upsides to using a dehumidifier.
Some (all? most?) dehumidifiers can accept a hose connection in place to the collection bucket, my parents have one on a raised shelf in their basement and have the hose drain in the laundry sink -- no need to empty the bucket.
Isn't running the AC constantly means the thermostat is stopping the compressor every time the temperature gets too low and starting it again when it becomes too high? If so, why is it better to run it constantly?
If other variables are constant, the dehumidification is proportional to air changes/air flow.
However, some of those other variables are not consistent across different designs. For example, they may use a different refrigerant that requires a different compressor. Centrifugal devices like fans and compressors use power in a non-linear fashion. Look up pychrometric chart and/or fan affinity laws for more detail
It runs for a longer time; the dehumidifying function of an air conditioner (the original use, thus the name) is a function of airflow x time, and airflow doesn't change much.
Does this mean that you could dehumidify a room very quickly by just vent-ducting a blower fan to your dehumidifier? Or is there a point of diminishing returns where the air must linger for a certain time within the dehumidifier to actually have any humidity extracted?
(Yes, I'm aware that such a set-up would be impractically noisy; it's just a thought experiment.)
