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Ask the Experts: Dehumidifiers

7 June 2010

“I rarely use AC so this seems to be the main driver of my electricity bill in the summer. Is it already time in the season to already have our dehumidifiers plugged in? What happens if we don’t use one? Besides buying a more energy efficient model, is there anything we can do to make it run more efficiently? Can I water my plants with the collected water without killing them?”

Hi Amie!  Thanks for sending in the question and reading the blog so faithfully!  I’ve been getting some more questions about dehumidifiers these days, especially after Minnesotans got the taste of 65% and higher humidity.  Reducing humidity in our homes keeps us comfortable and cuts down on musty, odd odors that can come from high humidity.  And, as Amie points out, keeping low humidity also helps us run our A/Cs less often and save money in the summer.  So here are the top four points for smart dehumidifier use:

Above 70 Degrees – If you start running your older dehumidifiers before the temperature gets over 70 degrees, you’re shooting yourself in the foot a bit.  Because of the way that dehumidifiers remove moisture from the air, if it’s below 70 their coils will freeze, causing them to use electricity without any measurable benefit to you or your home.  Remember to clean out the filter before you get it started!

Below 60% Humidity – Many Minnesotans live without running dehumidifiers.  However, if you get above 60% humidity in your basement, your comfort won’t be the only thing to suffer.  That can cause moisture issues – and if you have anyone living in the basement or storing papers and clothing down there, it can get pretty unpleasant pretty quickly.  If your dehumidifier doesn’t have a humidistat built in, you can find one reasonably priced at most hardware stores to hang nearby so you can measure the relative humidity.

Water With Caution – As far as watering your plans with the collected greywater goes, I’m giving you a cautious go-ahead.  The water collected by your dehumidifier isn’t filtered and can collect copper and zinc from the coils.  I suggest a little experiment – try using this water on non-edibles, like houseplants, flowers or perennials, next to a control plant that isn’t getting any dehumidifier water.  If they both do fine, you’re good to go!

New and Shiny – If you’re spending a lot of money to run your dehumidifier, it never hurts just to look at newer ENERGY STAR-rated dehumidifier.  I’ve found a couple good models for under $200 that come with low-temperature operation (no freezing coils!), an automatic humidistat and plenty of capacity to take care of your basement.  The best way to decide if it’s time for a new model is to look at operating costs – how much is it costing you a month to run your dehumidifier?  And how much would it cost to run an ENERGY STAR dehumidifier?  If the operating costs of the new unit is less, it may be time.

Good luck – and let me know if you have any more questions!

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