Michigan State University Extension
Preserving Food Safely - 01600534
10/13/97

ENERGY COST OF DRYING

  Let's calculate the energy cost of drying green beans  and
peaches in a dehydrator built from plans in Home And  Garden
Bulletin   No.  217,  pages  16-20.   The   dehydrator   can
accommodate 18 pounds of fresh product.  Assume that  during
the  first  2 hours of drying time, all nine  75-watt  light
bulbs  (675 watts total) will be on.  Only six  light  bulbs
(450  watts total) will be left on for the remaining  drying
time.  Calculate  the energy cost at 5 cents  per  kilowatt-
hour.                                                       

GREEN BEANS                                                 
  18 pounds = about 9 quarts                                
  Drying time is 8 to 14 hours (average = 11 hours)         
  2 hours x 675 watts  = 1,350 watt-hours                   
                       =  1.35 kilowatt-hours               
  9 hours x 450 watts  = 4,050 watt-hours                   
                         4.05 kilowatt-hours                
  1.35 kilowatt-hours + 4.05 kilowatt-hours                 
    kilowatt-hours     = 5.40                               
  It takes 5.40 kilowatt-hours of electricity to dry about 9
quarts of green beans.  That's equivalent to 0.60  kilowatt-
hours per quart.                                            

  0.60 kilowatt-hour x 5 cents/kilowatt-hour = 3.0 cents    

  The energy cost of drying one quart of green beans is  3.0
cents.   (This   does   not   include  the  energy  cost  of
blanching the beans as pretreatment for drying.)            

 PEACHES                                                    
  18 pounds = about 8 quarts                                
  Drying time is 36 to 48 hours (average = 42 hours)        
  2 hours x 675 watts  =  1,350 watt-hours                  
                       =   1.35 kilowatt-hours              
  40 hours x 450 watts = 18,000 watt-hours                  
                       =  18.00 kilowatt-hours              
  1.35 kilowatt-hours  +  18.00 kilowatt-hours              
      kilowatt-hours    =  19.35                            

  It takes 19.35 kilowatt-hours of electricity to dry  about
8 quarts of peaches, or 2.42 kilowatt-hours per quart.      

  2.42 kilowatt-hours x 5 cents/kilowatt hour = 12.1 cents  

  So the energy cost of drying one quart of peaches is  12.1
cents.                                                      

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