Yup. Pretty much the same. There is almost nothing to be done about sealing windows and whatnot (they are actually sealed very, very well but the point is I cannot modify the building).
There is a second transitory factor I did not mention.
If your residence has had low humidity for months and months and maybe years and years, all the drywall and furniture are themselves desiccated. And as they’re exposed to more humid air, they will try to absorb that moisture to reach equilibrium. Same is true for wooden flooring, cabinets, clothing, etc. Anything not made of stone or plastic is absorbtive and will pull newly induced humidity out of the air and into themselves.
With the result that you’ll be pouring gallons of water into them all until they reach your desired more humid equilibrium. You might need X/gallons per day of humidifying capacity to get to your target value any time this year, but once arriving there, be able to maintain that target value on maybe 80% of X gallons per day.
The tighter your envelope, the larger the relative contribution of one-time re-humidifying your contents. With a leaky envelope, you’re mostly actually trying to re-humidify the outdoors. Which task is so immense as to be immovable.
I have both an AC that functions as a dehumidifier, and also a device that removes moisture and releases heat in doing so. Just as there are a variety of types of humidifiers, there are a variety of types of dehumidifiers.
If you have a hot air source in your home + a place to put something in front of that airflow, I may have a cheap and fairly effective solution. I use it for my pellet stove, I have a tray table set about 3 feet in front and set up a 2 in deep tray of water where I placed a humidifier wick for a very large humidifier, specifically this wick:
That set up gets about 3 gallons per day into the air, it would get 4 but one water addition would be during the night sleeping time. A larger tray would also solve this, but 3 gal/day is enough for my home.
Unless you’re talking about chemical cartridge style dehumidifiers, a dehumidifier is just an AC with both the hot and cold side of the heat pump in the same room. You technically could make a dehumidifier out of a portable AC if you just kept the output vent inside the room as well, it just wouldn’t have the built in humidistat to turn off automatically.
Yep. But that’s still darn useful in humid environments.
My complaint here in hot humid south Florida is that to achieve dry-ish air indoors during spring, summer, or fall, using a pure HVAC system, buildings need to be cooled to about 68F. I did not move to the hot part of the country to need long pants, long sleeves, and a sweater to avoid freezing indoors. But that’s my general experience around here. Everyone jokes about carrying a restaurant sweater in their car, so it’s not just me.
In essence building managers and homeowners adjust the AC temperature up or down as needed to get their desired humidity level and learn to tolerate the arctic indoor temps that result.
It’s far smarter, and has much cheaper operating costs, to set the AC thermostat to the temperature you want, then use a separate dehumidifier controlled by a humidistat to remove the excess humidity. That way one can have shorts & t-shirts compatible indoor temps in the upper 70s and also have low humidity. Which is what our winter weather outside is like; the weather people come from all over the world to experience.
But it does require additional capital expenditure up front which is why substantially no homes or business have that built in.
Errr, or many of us like temps from 68°F through the low seventies. High seventies are too hot. You get there because it’s expensive (in money and greenhouse gasses) to cool your home to a comfortable temperature. 
I have dehumidifiers in the basement because they are cheaper than air conditioning the basement. I also installed a nice HVAC system in the finished part of the basement recently, and i love it. It means i can use that space in the summer. But i still dehumidify some areas that the HVAC doesn’t reliably keep dry.
Yeah, that’s a consequence of improper, cost cut, HVAC design, not an intrinsic property of HVAC. Unfortunately, the US seems structurally terrible at educating HVAC designers on basic principles of the system.
Oversized HVAC systems have a problem dehumidifying as there’s a natural lag between HVAC which starts cooling the air immediately and when it starts dehumidifying where the coils get substantially below the dew point of water long enough that water is able to drip off the coils (5ish minutes). Large, bang bang style systems will be on for like, 5 minutes every hour which means substantially no dehumidifying gets done and people don’t understand this which means they lower the thermostat just so the system turns on for 10 minutes every hour.
Heating systems, it’s fine to oversize and undercycle so HVAC installers just use extremely simple formulas, apply a big fat safety factor on top and install grossly overcapacity heating systems. Cooling systems actually require detailed modelling of heat flows and every owner is afraid of installing an under capacity cooling system so plenty of places have grossly overspecced cooling systems that are fantastic for controlling temperature because you can get down to your target temp within minutes but ineffective at humidity. Fixing this would require training a bunch of HVAC contractors on software to model heat flows that they aren’t interested in learning. Furthermore, the business model of HVAC contracting is they sell by the ton of cooling. An innovation that correctly sizes units runs directly counter to a salesperson’s business interests.
Additionally, lowest cost HVAC systems are single speed, on/off compressor designs. The speed at which you move fans over the coils determines the degree of humidification vs cooling. Slow fans speeds dehumidify more for a given unit of cooling. By controlling both the fan speed and the temperature of the coils, you can get to almost every combo of temperature and humidity.
Running a dehumidifier inside of an AC system is an offense to God and good taste but I can see for some people, why it feels like their only choice.
Thanks for the education. Always good to hear from a pro.
In my personal home case the HVAC system seems well-sized to the cubic footage and typical desired temperature delta from the hottest of days. My challenge is entirely that I like it a lot warmer inside than most people. And as such the HVAC doesn’t run much, and when it does, the the high temp means the air’s water capacity is such that there’s still more humidity than desired in the rooms.
Personally, I don’t mind highish humidity. 78F & 75% is fine w me; very cozy in fact.
But the risk of mold is significant when you run both high temps and highish humidity. So to keep me happy with the temp and the landlord & my stuff happy with low enough humidity to prevent mold, I need to separate the two concerns with two machines acting separately on the two aspects of the problem. So 78F & 50% humidity, and lots of water per hour being removed by the dehumidifier.
Does your HVAC remote have a “dry” setting? Dry will still cool the room, just the minimal amount possible while still removing moisture. Check to see where you sit temp wise just running dry. If it’s above your target temp, try look to see if your HVAC has a “sleep” setting for cool. Sleep will run the fans as slow as possible while still hitting your target temp. However, it will auto turn off sleep mode after some number of hours. Finally, try running it with a slightly lower temp than you prefer but with fan speed set on low. This will ensure the compressor stays on as long as possible, hopefully at a 100% duty cycle but at an equilibrium closer to your desired 78F.
It’s probably actually better to use your HVAC to get your humidity to desired levels and then a cheap space heater to adjust the temp than what you’re doing running both a dehumidifier and a HVAC. At the very least, it stops you from having to dump water manually.
From the perspective of the OP and all those who live in cooler climates where the indoor air is very dry in winter, the thing to do with steam humidifiers in summer is unplug them and put them away! Winter is the only time you need them, and the added heat is a benefit, though electricity is typically an expensive way to create heat.
No can do Kemosabe.
It’s a modern, but low cost dumb HVAC with an extra dumb 'stat. Thermostat has three modes: “off”, “heat”, & “cool”, and one temperature setting. Fan is either “on” 24/7 or “auto” where it runs while the stat calls for heat or cool, and not when not. No ability to get fancy with that rig. And no ability to replace either the HVAC or the stat; it’s a rented apartment.
At least I was able to route my dehumidifier drain line into the HVAC condensate drain line. Otherwise in summer I’d be emptying the 1.5 qt reservoir almost hourly.
My basement minisplit (newer than the dehumidifier) has “dry” setting, but if i run it on that, the basement gets really cold, even by my standards. I don’t really want the basement to be in the low 60s in the middle of the summer.
Also, i don’t dump the water from the dehumidifier in the other room. It has a pump, and i have it pump the water through a little tube, and up and out a window. It waters a rhododendron.