CUTTING PAPER - IDEAS - Default duplexing
 

How much can 'Default Duplex' save?

If you set your copier to default to duplex copies, how much paper might you save?  The best estimate at present is that you would reduce paper use in the copier by about 10%, though you might save more. 

At LBNL, we measured actual savings from default duplex on two fairly new 50 copy per minute copiers.  Both copiers were installed with default duplex disabled (that is, 1:1 copying was the default).  We left the copiers in default single-sided for several weeks, then enabled default duplex, and continued the measurements for several months.  The figures below show the results. They both show the "duplexing rate" — the fraction of images that are on duplexed sheets.
 
 
 
 
Figure 1: The machines were in default simplex time for about one month and in default duplex for several months.  The two copiers are identical models, in similar office environments.
 
Figure 1 shows the average duplexing rate in the entire 'before' and 'after' periods.  Figure 2 shows the same copiers but showing the duplexing rate for each 2-week period. 
 
 
 
Figure 2: The x-axis is the number of images made and so corresponds to time.  Each "stairstep" represents about 2 weeks.  The duplexing rate shown below 20% is almost certainly a data collection error, as the data point before it is also suspiciously high.  The errors cancel each other out when calculating the duplexing rate for the entire period.
 
 
 
Default duplex raised the duplexing rates by about 15% on the two copiers, reducing paper use by 10%.  The discussion of duplexing rates explains why these two percentages are different.

There are a few reasons why you might save even more.  The duplexing rates in default simplex were already quite high—the only national estimate of duplexing rates has this speed of machine at 18%.  If your copier’s duplexing rate is lower than ours, then you have a lot more potential savings.  The copier model we used duplexes at only 60% of its simplex speed (30 cpm in l:2 duplex mode; 50 cpm in l:1 simplex mode); many copiers duplex faster and so encourage more duplexing.  Also, nothing else was done to affect duplexing behavior, such as simply putting up reminder signs,  which a separate study found increased duplexing rates.  On the other hand, this copier is a relatively reliable model, less prone to jamming, and so people have fewer bad experiences to discourage them from duplexing.
 
 
 
     Duplex Rates