a few thoughts on operations research and coffee

A blog post about espresso machines by John D. Cook got me thinking about coffee.  In this post, John writes about two approaches to making good espresso:

  1. Investing in good equipment and good techniques lead to better espresso and the satisfaction of mastering the espresso-making process.
  2. Making good espresso is fraught with expense and peril– espresso machines take years to pay off, and many things that can go wrong with the machinery.

The first approach is a case for owning an espresso machine. The second approach is a case for not owning an espresso machine and instead going to a decent coffee shop on a daily basis.  Both approaches are valid, and they reflect different values. I’ve made similar decisions.  My three main values for coffee evaluate (1) cost, (2) taste and (3) convenience.

I like coffee.  I like it so much that I have often used operations research to make coffee-related decisions (although to be honest, it’s mostly glorified arithmetic).  I haven’t blogged about it yet. Here are the main coffee-related decisions I have made in the past five years:

  1. I decided to continue to make my own coffee rather then purchase the coffee available in the department for $0.35 per cup.
  2. I decided to continue to make my own coffee rather then purchase coffee from a coffee shop on the way to work.
  3. I decided not to buy a Keurig coffee maker for my office.

The first decision was a simple cost-benefit analysis: I could make my own coffee for less than half as much as the office coffee club charged.  But the decision wasn’t purely based on money: the department only had powdered creamer. That was a problem.  Since I made this decision nearly five years ago, I buy better, more expensive coffee beans that cuts away at most of the savings from making my home-brewed coffee. When consider both cost and quality, continuing to make my own coffee is a no brainer.

I now spend a lot more per cup of home-brewed coffee since I buy better beans (it costs me about $0.47 – $0.63 per mini-pot, which is about two mugfuls. And yes, I made a spreadsheet for that.) Making coffee myself costs a lot more now than it did when I did my original analysis.

After I had my second child, I made my coffee at home and brought to work in a big mug.  I love my coffee maker, but its reusable filter was a little bit of work to clean every day.  I wondered if buying an equally good cup of coffee on my way to work instead was a good idea, paying for convenience (there are two good coffee shops on my walk into work, plus other shops that I could easily pop into along my commute).  After a few test runs to coffee shops on my way to work, I determined that it took more time to buy a cup of coffee than to clean my coffee pot and filter at home.  So while I don’t like cleaning, I like waiting in lines even less.  I would be willing to wait in line for Dunkin Donuts coffee, but the nearest Dunkin Donuts adds 15 minutes to my morning commute. It’s hard to justify making that trip every day (I can get a lot done with an extra 15 minutes every day!).  I now make coffee using either Dunkin Donuts or Rostov’s coffee beans (which are roasted on-site here in Richmond).  This increases the cost of my coffee while improving quality and convenience.

A year ago, I once again got sick of cleaning my coffee pot and entertained the idea of buying a Keurig coffee maker to keep in my office.  I’ve had coffee from other people’s Keurig coffee makers and was impressed with the quality of the coffee they made.  It would cost more per cup, but it would still cost less than buying coffee in a coffee shop, it would make delicious coffee, I wouldn’t have to tote coffee mugs to and from work each day, and I wouldn’t have to clean my coffee pot every night.  After reviewing Keurig coffee makers extensively, I opted against owning one for the following reasons.  First, I am choosy with coffee.  There are fewer types of coffee available in K-cups. I cannot buy Dunkin Donuts coffee in K-cups (at least at the time), and many of the K-cups contain dark roasts (I prefer medium roasts).  In addition, I couldn’t control how strong the coffee would be made.  To mitigate the first problem, I checked out the washable filter for Keurig coffee makers that can be filled with any coffee.  The reviews indicate that it doesn’t work very well. In addition, it would need to be washed every day, canceling out one of the benefits of owning a Keurig coffee maker.  I would have been willing to pay more per mug of coffee as long as the quality stayed the same and the convenience improved, but this isn’t possible.

I brought an old coffee maker from home to keep in my office. I now sometimes make decent coffee using this cheap-o coffee maker using disposable filters when I don’t want to bring it in from home.

I’ve discussed three criteria for six different coffee options.

  1. cost — cost per day (minimize)
  2. quality/taste — a 1 to 10 scale where 1 is the worst coffee I have tasted and 10 is the best
  3. convenience — a scale measured in minutes of inconvenience per day, where a 0 represents coffee that I do not have to clean up.

I’ve inserted pictures that consider two tradeoffs at a time.  When considering only convenience and cost, only making coffee in my office using my cheap-o coffee maker and drinking the department coffee make sense. When considering taste and cost, only buying Dunkin Donuts coffee, making quality coffee at home, and making coffee in my office make sense.  However, none of the coffee options is dominated when considering all three criteria. I suppose I should apply multi-objective decision analysis to make my final decision.

I have written about coffee here and not espresso.  The last decision I have made didn’t make the list but is worth noting:  I decided not to get into espresso drinks. Don’t get me wrong, espresso is delicious.  But it’s expensive, and I avoid expensive habits.  I drink espresso as a special treat now and then.  Maybe I should live my life a little more fully and drink espresso daily, but my thrifty nature is an important part of who I am.

8 responses to “a few thoughts on operations research and coffee

  • Paul A. Rubin

    You need a multiattribute utility function to properly capture trade-offs, particularly as you probably have a strictly concave function (marginal utility of flavor decreases, marginal disutility of cost increases).

    I’m partial to good coffee and a French press (a metal one — I keep cracking glass ones). I nuke the water in a microwave while cleaning/filling the press, and read e-mail (or your blog 🙂 ) while it steeps, so the process is not too time consuming. Purists would use distilled water, but my taste buds aren’t that sensitive.

  • Christian Muise

    I don’t have the hard numbers to put forward (can’t find the back-of-the-napkin that I originally used), but I would make one suggestion that reduces costs and increases quality: roast your own.

    A hundred bucks or two gets you a decent entry level roaster, and it is extremely simple once you get the hang of it. Green beans last years (so you can buy in bulk), and the difference in taste is huge (roast what you need for the week, and it’s always fresh).

    At the amount my partner and I consume, I think the roaster paid itself off in about a year. Definitely worth it.


  • Greg Glockner

    Seems to me that the next cut at the data should look at combining cost, taste and (in)convenience in a single chart. Much easier to – ahem – digest that way. There’s probably an efficient frontier of coffee choices. (Seems like the start of an undergraduate case study).

  • Laura McLay

    Greg and Paul, Your suggestions are great! I didn’t include the 3D chart, since I couldn’t figure out how to create one while maintaining the labels. However, none of the options listed are dominated (it’s not clear in the 2D figures that all choices would be on the efficient frontier). I could be wrong, seeing as how tired I was when making the figures. However, some of the choices *felt* dominated to me. I would have done a multiattribute utility analysis if I were blogging these days with a snuggle little baby in my arms. My analysis in this post should give me everything I need to create meaningful ranges for the weights (assuming a MAU function that is additive).

  • Laura McLay

    Christian, I am going to look into roasting my own beans. I once roasted barley in my oven (I heard it was a good coffee alternative), and it was *fantastic* although I couldn’t evenly roast that way. A roaster would control the variables better, and it would give me the pleasure of having another DIY adventure in the kitchen. I started buying coffee that is locally roasted here in town, so my coffee is much fresher–although not as fresh as yours–and the difference is noticeable. (Here is the part where I confess that I no longer grind my beans on a daily basis–I grind the whole bag at once. I’ll look into home-roasting as soon as I can manage daily grinding again!)

  • Laura McLay

    Paul, I am ashamed to say that I’ve never had French pressed coffee before. That gives me a second new coffee alternative (the first being to buy a roaster and make coffee from home).

  • Paul Rubin

    French press and home-roasted are not mutually exclusive. I think a French press is better than a typical drip coffee-maker, but not as good as the high end coffee machines.

    I buy beans from a local coffee shop (they throw in a large drink, any type, free, which makes it quite cost effective), keep them in an airtight bag in the fridge, and get pretty good coffee. I now let them do the grinding, but I used to grind my own each morning, which makes them *slightly* fresher.

    According to a little research I did online, water temperature during brewing is one key. You can pick up some general brewing tips by looking at reviews of coffee-makers.

    Or you can learn to like Cuban coffee. (I had a Cuban teammate in college.) Easy to tell when it’s done: stir with a metal spoon, and if the spoon starts to dissolve, it’s ready.

  • Thiago Serra

    I had a similar issue for bread machines.

    However, for a young couple that stay just a few hours daily at home, it would take at least two years to amortise the investment alone (not to mention electricity and raw materials) and I’m very skeptic about how long a machine like that would last.

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