## 11 comments on “buying a new washing machine, a quick multiobjective analysis”

1. Where did power consumption come in? With increasing energy costs this would seem to be an interesting component of the problem.

2. That is a good point. I figured that doing the same amount of laundry would lead to *roughly* the same energy costs. We compared front loaders, which all use way less water than the top loaders. Energy costs over a year pale in comparison to the purchase prices. Over time, that might not be true. If I spent more time on this analysis, I would have taken energy into account.

3. Nice application of DA and sensitivity analysis. Will share this with my undergrad students this semester.

4. Thanks, Chris. They should really improve upon this analysis! Let me know what they would do differently.

5. Peter, check out this spreadsheet to see the energy costs per year. At five loads per week, the energy costs are \$42 for an energy star washer vs. \$85 for a conventional washer. I was only comparing front loading energy star washers, so the energy costs would average out to be roughly the same. Had I added a conventional washer to my comparison, I would have needed to add in energy costs. Thanks again for your feedback!

6. Laura – I mentioned my stress over buying a washing machine to a grad student and he led me to your blog. This is great – what did you end up buying?

7. Karen, We ended up buying a Whirlpool, I think it was model WFW9151YW or maybe WFW9351YW.

8. Hi Laura – thanks for the great example. I have 2 quick questions about the maths behind the exponential utility function in your spreadsheet, and I hope you can share a little time to help me understand it.

You used the maximum and minimum payoffs in order to calculate the value of the utility function. Then you state the value of rho (or R). (1) How did you derive this?

You use a sort of ‘middling’ value in the range between max and min payoffs. (2) Why did you do this, and how did you arrive at these values?

Many thanks! I’m hoping to build one of these myself soon to support a house-buying decision.

9. Paul, Thanks for the comments. To be honest, I don’t remember a lot of the details. I used “Strategic Decision Making” by Craig Kirkwood as the text – the values of rho (or R) comes from that text. To answer your broader question about doing an analysis for buying a house, I recommend “Smart Choices” by Hammond, Keeney, and Raiffa as a gentle introduction to building models to help with buying a house. I may do that this year too!