What is the the “cost” to operate a dehumidifier if the cost of conditioning the added heat is factored in?
I am looking at using an off-the-shelf stand-alone unit (Frigidaire/Eletrolux 70 pint/day) it has an Energy factor of 1.8 L/kwh. I could easily locate it in an upstairs utlity room and drain it into the washer-box.
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John,
I believe from a comfort and air quality standpoint, most homes could benefit from supplemental dehumidifcation, those built in arid regions being the exception. The need is actually greater in areas that are humid, but not quite so hot, like a great deal of the midwest. My preference to address this is to install a slightly undersized AC system. (When it reaches 100 at my house in N.IL, my main system will not cool much below 80, but the RH will be in the 40's and I can live with that for the half-dozen days that occurs.) One the many days when conditions don't require much if any central system cooling, the portable DH units can help a great deal.
The heat generated from most portable residential humidifers is MOL equivalent to two regular refrigerators (or less). In other words, in all but the smallest spaces, insignificant.
The drawbacks for these units is drainage, noise and having the unit occupying space in someplace you'd rather not have it. You seem to have those issues addressed.
Another option is the "Inline dehumidifier". I have no personal experience with these units, but like the concept. They are actually a "sidestream" unit, that is installed on the central system ducting. If you have a minimum air flow setting, availalable on the varaible speed furnace/air handlers, the unit is run continuously except when the main unit is in cool mode or locked-out via a humidistat that prevents the unit from working when humidity is below a preset level.
As Tim suggest, properly-sized ac shouldn't generally need supplemental dehumidification. Here, there's a brief period when the humidity's high and temps aren't. Most don't do anything.
We use a stand-alone unit (whichever one I've recently bought used) in our incoming airstream. Units designed for that strike me as unreasonably expensive. Not difficult to cobble some sheetmetal for adapting the stand-alones. Mine lives outside, leaving much of the heat gain there. Newer stand-alones, btw, are more efficient than the older ones that used to really heat up a room.
Our house has no need of ac, but everybody needs dehumidification here. Our added electric cost this time of year is ~$1/day. Would be less with fewer air changes. We're .5 ACH.
A similar client house got an air source heat pump to facillitate financing. Turns out it's ac is primarily dehumidifying, similar operating cost, same interior house temp. Obviously purchase price was considerably more than the $50 I generally spend.
PAHS works. Bury it.