Reusing Ziploc bags: Eco-friendly, but does it save money?

Saving Pennies or Dollars is a new semi-regular series on The Simple Dollar, inspired by a great discussion on The Simple Dollar’s Facebook page concerning frugal tactics that might not really save that much money. I’m 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’re 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’t 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’s not something I like to do if I can avoid it.

Another “right off the bat” point: I should point out that in an earlier post, 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 “not worth it” camp from a purely financial standpoint.

Here’s 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’s not a terrible savings, but it’s not a home run, either. For a lot of people, the reason for rewashing such Ziploc bags isn’t the financial savings, but the environmental benefit. However, it’s 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’ll be the first to admit that my fifteen seconds per bag isn’t particularly dextrous), the better your savings rate is.