by Ethan Johnson
July 11, 2008

Some years ago, I started to notice that HGTV was quietly removing ceiling fans whenever a total room makeover was being performed. I wondered if running the ceiling fans in our house was something of a sucker's bet, as the AC might actually cool the room more efficiently, and who knows what the electrical draw of each fan is, anyway?

I turned off all of our ceiling fans, and our electric bill dropped noticeably. I assumed that this meant that a) our ceiling fans were huge energy hogs, and b) our AC unit was a model of efficiency. Well, our AC unit is proudly inefficient, so now that I have the magic formula for determining how much electricity we're using at any given time house-wide, I ran an experiment to determine what our best cooling strategy is during these brutal summer months.

The test plan was to turn items on or off (see testing notes) and use a stopwatch to gauge how quickly/slowly the electric meter disc turned as a result of the changes. I measured each reading twice to check for data consistency.

Impuse Power (Very few electrical items running, including 2 refrigerators, AC unit off)

Test 1: 60 seconds

Test 2: 59 seconds

Average: 59.5 seconds

Electricity usage: (7.2 * 3600)/59.5 = 435.63 W

Two electric fans on (1 running on "high", the other on "medium")

Test 1: 53 seconds

Test 2: 53 seconds

Average: 53 seconds

Electricity usage: (7.2 * 3600)/53 = 489.06 W

One ceiling fan on (Moderate speed, electric fans off)

Test 1: 63 seconds

Test 2: 63 seconds

Average: 63 seconds

Electricity usage: (7.2 * 3600)/63 = 411.43 W

Note: Our electricity draw seems to fluxuate, which is why running a ceiling fan magically drew "less" electricity than the impuse power reading above.

All ceiling fans on (Moderate speed, electric fans off)

Test 1: 54 seconds

Test 2: 51 seconds

Average: 52.5 seconds

Electricity usage: (7.2 * 3600)/52.5 = 493.71 W

All fans on (Same settings for all fans as noted above)

Test 1: 43 seconds

Test 2: 43 seconds

Average: 43 seconds

Electricity usage: (7.2 * 3600)/43 = 602.79 W

Air Conditioner only (All fans off)

Test 1: 51 seconds per 10 revolutions = 5 seconds per rev

Test 2: 50/10 = 5 seconds

Average: 5 seconds

Electricity usage: (7.2 * 3600)/5 = 5184 W

Conclusion:

Good thing we don't "just" run the air conditioner to keep the house cool. The air conditioner alone, if allowed to run 24 hours a day for 30 days, would contribute 3600 Kwh to our monthly electric bill. Remember, all other electrical items ADD to the total cost. In August 2006, we rang up nearly 3700 Kwh for the month, to the tune of $528 USD. Clearly, our air conditioner should be the cooling method of last resort.

As an experiment, I have set our thermostat to a whopping 85 degrees (F). All of the ceiling and electric fans are on. Supposedly, by using the overhead and desktop fans to augment our climate control, we can get the same cooling effects this way as we would from solely running the AC. As I write this, we're about 2-3 hours away from Peak Heat. Here goes nothing!

I'll report back as climate control adjustments are made. Historically, our next electric bill is one of the year's highest, with August/September being the worst. Whatever we can do to reduce our energy consumption and/or be smarter about it is imperative.

Before you crank the AC this summer, try this test for yourself. Are you sure an electric fan isn't the better option? <EM>

(More articles like this one may be found here.)