Posted by: Li Ling Young | July 7, 2013

We Need a New Dehumidifier

A basement is a hole in the ground that you cover with a house.  I don’t know why we have basements in the Northeast.  They probably started out as a little dug out spot under the house to store veggies, and then, when we started having plumbing, electricity and, later, central heating, grew into a room-sized space for pipes, wires, big, noisy, smelly machines, and, later still, a bunch of stuff we thought we needed but really don’t so now have to store somewhere clean and dry.

Our basement, like most basements the world over, is kind of wet.  We don’t get water in our basement: that would make it actually wet.  Ours is just sort of damp in the summer.  Our basement is damp because it’s cool down there.  Cool things are always wet.  There’s really no way to dry out something that’s cold because drying means evaporation and evaporation takes energy, which is in short supply if you’re talking about something that’s cold.

To reduce the dampness in our basement and keep things from getting smelly, we dehumidify the air down there.  When it’s either very warm or very humid up above ground, humidity in the basement goes way up, and that’s where our wetness comes from.  Our dehumidifier removes moisture from the air by the same refrigerant cycle I described for the heat pump.  The dehumidifier we brought with us from our other house pooped out on us this spring, so we had to get a new one.  By the time I got off my duff and chose one, the humidity in the basement was 88% RH: way too high!

I wanted the most efficient dehumidifier available, so I went to the ENERGY STAR website and looked at the list of ENERGY STAR labeled dehumidifiers.  The most efficient dehumidifiers have an energy factor (EF) of better than 4 litres/kWh, and the least efficient ENERGY STAR labeled dehumidifiers have an EF of less than 2.  Glad I looked into it instead of just buying an ENERGY STAR dehumidifier from Sears, which is what I did last time, I set about shopping for the dehumidifiers at the top of the list.

First, I had never heard of any of the manufacturers: Santa Fe, Quest, Ultra-Air…  That’s because these super-efficient dehumidifiers are made for places like Louisiana where they don’t just perch their houses on top of a big hole in the ground; they perch their houses on top of a little hole in the ground, also known as a crawlspace.  The problem with crawlspaces is they haven’t evolved much past the root cellar stage.  Whereas basements are kind of wet, crawlspaces are actually wet (often), and they can get really smelly and make the house more humid than would otherwise be the case.  With no comment about the abysmal state of building science in cooling climates, let me just say that the dehumidifiers at the top of the list were made for climates where dehumidifying is as big a deal as heating is in my climate.

How did I discover this?  Second, these dehumidifiers are literally ten times the cost I was expecting: about the cost of a cheap boiler.  No one here carries these things, but if I did want to order one, they’d be $2,000-$4,000.

I wasn’t ready to quit yet.  Since we’re living in the Energy Freakshow I thought maybe we could justify the !?$2,000?!? dehumidifier.  Time for some math.

The old dehumidifier had a 2- to 2.5-gallon reservoir (remembering and guessing).  We never set the thing up to automatically drain itself, and I liked that, despite the daily inconvenience of emptying the bin, because it allowed me to keep track of what the humidity load was. We emptied it about twice every three days.  That means 5 to 7 litres per day.  Assuming the ENERGY STAR standard hasn’t changed since we bought our last dehumidifier, that would be around 3 kWh/day, which is consistent with what our home energy monitor told us: 3-5 kWh increase in daily electricity consumption while we were using the dehumidifier.

Three kWh per day for June, July and August is about 300 kWh.  If the best dehumidifiers are EF 4.2, and the baseline ENERGY STAR dehumidifier is EF 1.85, then we could potentially reduce our dehumidifier electricity to 142 kWh for the year, for an annual savings of 157 kWh.  Worth it?  How much does electricity cost?

Those who have been following the blog know we get our electricity from our solar panels, so in a way you could say our electricity costs nothing.  But that’s not helping us make a decision.  Let’s look at the prevailing cost of grid electricity in our town: 14.5 cents/kWh.  The 157 kWh/year savings represents $22.80 in electricity costs.  That makes for a 78.9 year payback.  Our last dehumidifier only lasted 7 years.

We don’t have an efficient dehumidifier.  We have an ENERGY STAR dehumidifier.  I’m a little disappointed, but also proud of myself for not buying the $2000 dehumidifier: in the way one is proud of oneself when one doesn’t take a second serving of dessert.  We ended up getting a basic ENERGY STAR dehumidifier, with contractor discount, for $170.  I’ll put the rest toward our new electric car.


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