# Consider a robot vacuum.

My wife and I recently acquired a robot vacuum. It has turned out to be a really great time-saving and life-improving investment. Some simple math suggests it may be worth you also considering buying one.

Let's say you spend 20 minutes a week vacuuming. That's about 17 hours of vacuuming per year. The Neato XV-11 costs about $350 bucks with basic shipping. For the purposes of our Fermi calculation we will say that your time spent vacuuming with the robot is zero. This is close to true. See below for exceptions.

At $350, if you value an hour of your time at more than about $20 you would be better off buying the robot than doing the vacuuming yourself in the first year. (17*$20=$340 - close enough for our fermi estimate)

Consider also that if you spend at least 20 minutes or less a week vacuuming, you can also instruct the robot to vacuum 20 minutes a week or more and raise the quality of your life by living in a better cared-for environment by some amount. For example, you could increase the pay-out of the robot by having it vacuum every other day.

If you have the robot do 60 minutes of work a week, then you'd only have to value your time at about $7 for the robot to be worthwhile in the first year. (52*$7=$364)

Do the calculation to see if it makes sense for you:

b = value of your time in dollars/hour

y = hours/year you spend vacuuming

350 = estimated price of a robot

x = b*y - 350

If x > 0, then the robot would save you money in time, according to how you value your time. If x < 0, then you either don't clean often enough or value your time so low that doing the work yourself makes sense. (So this is a simple model, feel free to make it more complex but the purpose of this post is to illustrate a fermi calc that seems to yield an easy choice.)

Given the cost of many upright vacuums, if you can avoid buying an upright and only buy the robot the calculation shifts drastically in favor of only getting the robot (and perhaps borrowing an upright if you really need one).

If vacuuming causes you particular disutility, you could put a dollar premium on that disutility and add it to b. On the flip side, if you really like to vacuum you'd want to discount b to reflect the extra utility you get from spending your time doing something you enjoy.

Considerations:

\- The robots are claimed to be pretty good at navigating complex room layouts. Our robot rarely (but sometimes) gets stuck behind places where it has little clearance to enter. You can adjust furniture layout to compensate or lay down (ugly) magnetic strips that stop the robot. You might want to try out the robot to make sure it can navigate your layout before you commit.

\- Once our robot failed to back itself fully into its charging dock and it ran out of juice and missed a scheduled vacuum session.

\- The robot won't drive itself off cliffs (down stairs to its doom). On the down side, it won't vacuum stairs. You may still need an upright to handle stairs.

\- You can make the robot do a lot more vacuuming than you would normally do yourself.

\- They are really quiet on carpet. Somewhat noisier on hard wood. Depending on your sensitivity, you may be able to run it while you sleep.

\- If you shed hair, you'll need to regularly clip the hair from the brush (like a normal upright). This takes almost no time. Do it as a part of the bin-emptying ritual.

\- It isn't clear to me how long the robot will last, so I don't know what the replacement period or cost is.

\- This is the robot we use, but there are many types. It isn't clear to me if the upgraded types are worth the extra money: [http://www.amazon.com/Neato-XV-11-Robotic-Vacuum-System/dp/B003UBPB6E/ref=sr\_1\_1?ie=UTF8&qid=1338882167&sr=8-1](http://www.amazon.com/Neato-XV-11-Robotic-Vacuum-System/dp/B003UBPB6E/ref=sr_1_1?ie=UTF8&qid=1338882167&sr=8-1)

\- I haven't investigated central vac, so I don't know what the trade-offs are. It seems like central vac still requires time to use and our goal was reducing time spent doing an automatable home maintenance task.

Maybe this is a trivial post, but I hadn't realized how much cleaner our environment could be or how much happier we could be for such a small relative investment. Much of the benefit comes from the robot being able to vacuum far more often than we'd ever have a desire to do ourselves.