海角大神

Saving Pennies or Dollars is a new semi-regular series on The Simple Dollar, inspired by a concerning frugal tactics that might not really save that much money. I鈥檓 going to take some of the scenarios described by the readers there and try to break down the numbers to see if the savings is really worth the time invested.

Calista writes in: Does reusing plastic (Ziploc) bags save pennies or dollars?

Clearly, any time you reuse something, you鈥檙e going to be saving money. The question is how much money and whether that time invested is really worth the money you saved.

Right off the bat, I would probably argue that the biggest reason for reusing sandwich and freezer bags is the environmental impact they have. These bags really aren鈥檛 biodegradable and when you toss them in the trash, they go into a landfill somewhere and sit there for a very long time. Think hundreds of years. That鈥檚 not something I like to do if I can avoid it.

Another 鈥渞ight off the bat鈥� point: I should point out that , I ran the numbers on rewashing and reusing Ziploc sandwich bags. I found that, for all of the effort of rewashing them using the dishwasher and reusing them, you only saved $1.42 per hour washing sandwich baggies. For me, this falls clearly into the 鈥渘ot worth it鈥� camp from a purely financial standpoint.

Here鈥檚 the thing, though: we do wash some of the Ziplocs that come through our house. Which ones? The quart and gallon-sized freezer bags.

The numbers At my local warehouse club, I can get a box containing four sets of 38 gallon freezer Ziploc bags for $10.74. This results in a price of $0.07 per bag.

I can also get a box containing four sets of 54 quart freezer Ziploc bags for $9.53. This results in a price of $0.05 per bag.

I can rewash and reuse a freezer Ziploc bag about sixteen times until the seams around the edge begin to give. This includes relatively short stints in the freezer.

According to my calculations, the cost to run a full load is 15.6 cents worth of detergent and water. A typical dishwasher load also uses 1.5 kilowatts of energy, adding an additional 17 cents to a load, bringing the total cost to approximately 32 cents per load.

I can fit twelve quart Ziploc bags (turned inside out and spread as widely as possible across the tines) and eight gallon Ziploc bags into a single dishwasher load. This inversion and insertion takes me about fifteen seconds per bag, which means I could in theory do 240 bags per hour.

This means that the cost of cleaning a quart freezer Ziploc bag is about 2.7 cents, and the cost of cleaning a gallon freezer Ziploc bag is about 4 cents.

Running the numbers You could either buy 256 gallon Ziploc freezer bags at a total cost of $18.09, or you could buy sixteen bags at a cost of $1.13 and wash them fifteen times each (which would require an investment of an hour of time) at a cost of $9.60, giving you a total cost of $10.73. Your savings for an hour spent washing the gallon Ziploc freezer bags in a dishwasher is $7.36.

What about the quart ones? You could either buy 256 quart Ziploc freezer bags at a total cost of $12.80, or you could buy sixteen bags at a cost of $0.80 and wash them fifteen times each (which would require an investment of an hour of time) at a cost of $6.48, giving you a total cost of $7.28. Your savings for an hour spent washing the quart Ziploc freezer bags in a dishwasher is $5.52.

Now, that鈥檚 not a terrible savings, but it鈥檚 not a home run, either. For a lot of people, the reason for rewashing such Ziploc bags isn鈥檛 the financial savings, but the environmental benefit. However, it鈥檚 good to know that you do save some money by rewashing them, and the faster you are at running them through the dishwasher (and I鈥檒l be the first to admit that my fifteen seconds per bag isn鈥檛 particularly dextrous), the better your savings rate is.