Your Mileage May Vary

Last week's Tip Hero newsletter contained this story on ways to "save big" on home heating costs. The title annoyed me right off the bat, because as I've observed before, the "big" savings articles like this promise are usually pretty trivial if you're not wasting money to start with. Sure enough, the first two tips in this article were simply stating the obvious: wear warm clothes and use warm bedding, rather than keeping the thermostat set at 80 all day and walking around in your shirt sleeves. The third tip, however, annoyed me for a completely different reason. It, too, was a fairly standard piece of advice that shows up in most articles of this type: use your ceiling fan to help distribute warm air so you can keep the thermostat lower. This tip shows up on all manner of energy-saving sites, from EnergyStar to the Daily Green, so I'd already seen it many times. My problem with it, however, wasn't that I'd heard it before; it was that I'd tried it before and it didn't work. The ceiling fan in our kitchen has one of those little switches to reverse the direction, so I set the ran to blow upward and turned it on at low speed, just as Michael Bluejay (a.k.a. "Mister Electricity," whom I normally consider a highly reliable source) recommends. Yet lo and behold, when I sat under it, I could still feel a draft, which naturally had the effect of making me feel colder rather than warmer.

I was frustrated to see this piece of advice trotted out yet again when, for me, it had been not only unhelpful but actually counterproductive. It was cited on so many trustworthy sites that I knew it couldn't be complete hooey, but I suspected that maybe it would only work well in certain circumstances—homes with high ceilings, for instance, where there's a significant difference in temperature between floor and ceiling. So I started searching around to see if there were any sites that dug deeper into how and when this tip is actually supposed to work, and I quickly discovered that there is almost no actual data on the subject. The sites that recommend it simply state as a fact that it works; they don't cite any studies to show that it works, or how well it works under different circumstances. Googling phrases like "studies fan use ceiling height" turned up nothing, and "winter fan use 8-foot ceiling" yielded only a couple of sites that say winter fan use may not be effective with low ceilings. An article from This Old House noted that "some authorities argue the benefits can't be felt in rooms with standard 8-foot ceilings," and one from Clark Public Utilities cites an "energy counselor" who says, "If you use a fan on an 8-foot-ceiling in the winter, even with the direction switched, it will merely create a cooling draft." A site called Use Electricity Wisely even declared outright that it's a "myth" that fans on a standard-height ceiling can help with heating, pointing out that "If you have a forced-air furnace and a well-insulated house with eight-foot ceilings, there will be little difference in air temperature from the floor to the ceiling." However, these sites, like the ones that support fan use, didn't provide any actual data to back up their claims—so it was simply a case of he said, she said.

Frustrated by the lack of useful information, I decided to send my story directly to Michael Bluejay, my usual go-to guy on any question related to energy use, in the hope that maybe it would prove instructive to others. I wrote:

I strongly suspect that this much-touted piece of advice is really useful only in homes with high ceilings, where there is a significant difference in temperature between floor and ceiling...I have searched for studies on the effects of winter fan use in rooms with different ceiling heights, but sadly, none of the sites that recommend the use of fans for heat distribution appear to have any actual data to back up the recommendation. Even the MythBusters have never addressed the issue of ceiling fan use, except to demonstrate that you can't be decapitated by one.
So at this time, I can offer only a single data point (mine) to counter the theory that ceiling fans are useful in wintertime with a standard-height ceiling. However, I would consider it only fair to point out that I have yet to see even a single data point showing that ceiling fans actually *are* useful under these conditions.

He sent me this response:

It’s worked for me, in multiple residences, none of which had tall ceilings.  The fact that hot air rises isn’t in dispute, nor is the fact that aiming a fan at the ceiling mixes the air in the room.  It’s entirely plausible that your particular fan in your particular room is making you cooler in your particular location.  If so, then yes, this particular energy-saving tip won’t work for you.

At first blush, this response sounds dismissive: "Well, okay, maybe it doesn't work for you, but it still works in general." But upon thinking it over, I realized that Mr. Electricity's response was actually making a very important point: what works for most people may not work for you. When evaluating energy use, there are a lot of variables to consider. Even something as simple as a ceiling fan can vary in its effects depending on the height of the ceiling, the speed of the fan, the shape of the blades, the temperature in the room, and maybe a whole bunch of other factors that we aren't even aware of. So the only way to know for sure whether it works in your particular situation is to try it.

It struck me that this is good advice not just for saving energy, but for pretty much anything, or at least anything having to do with money. I've noted many times that standard money-saving tips often cited as gospel, like using coupons or shopping only once a month or buying only used cars or avoiding credit cards, have proved unhelpful or even counterproductive for me. But the real problem isn't that these tips aren't good advice, at least for some; it's that they're presented as "one size fits all," as if they're guaranteed to work no matter what your circumstances may be. Yet in most cases, a more appropriate label would be "your mileage may vary"—a reminder that, while this guideline may be good for many people, or even most people, every person's situation is unique, and obviously, no one else can ever know the exact details of your own situation as well as you do.

None of this is meant to suggest that experts don't know anything and there's no point in listening to them. If they really are experts, they do know quite a lot about their own fields; what they don't know, and can't possibly know, is your personal circumstances. So the point is not to ignore money-saving tips, or to assume they won't work for you; it's just not to assume that they will. Instead, consider the advice from all angles, and think about whether there's anything in your personal situation that could make the advice either more or less useful, before deciding whether to act on it.