Tuesday, May 29, 2012

The AC is Sucking our Money

It's hot in here. To be precise, it's 85 degrees in my living room, and that's the coolest room in the house. In less polite terms, this would be referred to as "hotter than Satan's butt crack".

Did I mention that the humidity is through the roof? I can tell because I have an afro. I shouldn't complain, as the high water content in the air is probably the only thing keeping me from bursting into flame.

This sucks. I would put on the central AC, but it is broken AGAIN. The repair guy is coming, but not until Friday afternoon (when it's supposed to be only 67 degrees here).

Thank the Good Lord for my ceiling fans. We have one in each of the three bedrooms, and one here in the combined living room and kitchen (this is the one that will be switched out for the stronger one bought this weekend.

I'm going to use this opportunity to remind myself how much money I am saving when I don't use the air conditioner.

I've been distracting myself with research. Poking about in our records I see that the four ceiling fans we have use very little energy. The two bigger ones use only 82 Watts per hour (W/h), while the two smaller ones use 63 W/h. In contrast, the central air uses about 3500 W/h.

Did you know that fans only cool people and not rooms? It's true! I found it all over the inter webs! This means that I can shut off any fan in a room that's empty.

Here's some math about how much I'm spending to cool myself right now with the living room fan:

82 W/h = 0.082 kW/h
$0.06712/kWh x 0.082 kW/h = $0.0055/h

See that? That's a little over a half penny per hour.

If we ran all four ceiling fans at once (which would only happen if the four of us were in four different rooms) the math would look like this:

290 W/h = 0.290 kW/h
$0.06712/kWh x 0.290 kW/h = $0.0194648

Let's round up and call this 2 cents per hour.

Now let's look at how much it costs to run the AC:

3500 W/h = 3.5 kW/h
$0.06712/kWh x 3.5 kW/h = $0.23492

So, around this down to 23 cents per hour.

Hey, look! It's a ten-fold difference!
Let's look at the math for a whole day:

Four fans:

$0.019/h x 24 h = $0.456

That's less than 50 cents.


$0.23492/h x 24 h = $5.63808

Yeah. Over five and a half bucks. For one day. Hm.

This fiver looks different now, huh?

Now let's pretend that you did this for a month worth of days over the summer.

Four fans:
$0.456 x 31 = $14.136

Around 15 bucks.

$5.62808 x 31 = $174.47

OOOOhhh! So THAT'S why our energy bill explodes every summer! I get it now.

Does this mean that I won't be using my AC any more?

No. Not in the least. What it does mean is that I am only going to use it as a last resort. For example, when the temperature in the living room just climbed to 86 degrees. Oh, Lord.


  1. Ceiling fans only cool people if they're blowing down -- but they should have a little switch on them that reverses their direction, so that they'll blow upward, assisting in the "hot air rises" thing a bit. It helps the most if you have cool air coming from somewhere to replace the warm air being blown upward (fan blowing over a block of ice/bucket of ice can help some).

    1. Yes! This was one of the things I discovered when researching this post. Ceiling fans don't lower the temperature in the room, but they sure do make the temperature that's there much more bearable.
      I have been told numerous times that using the fans in the reverse direction on a low setting in winter can help us save money on heating costs, so we started this during the last few cold months.
      Years ago, when I lived in the tropics, I would wet a bandana and tie it around my neck to keep me cooler. It's a great trick to remember when you have to be outside all day in the summer.

  2. We don't have AC, so I tend to close the house down in the morning when the outdoor temp starts to rise, and draw the blinds-- just trying to trap as much cool air in the house as possible. It usually works pretty well-- right now it's 88F and sunny outside, and a cool-ish 75F inside. That might be a decent answer for days when it gets warm, but you don't want to run the AC a whole lot.

    1. We can make the downstairs pretty comfortable with the fan and some cold beverages, but the upstairs is HORRIBLE. Even by the time we put the boys to bed, it still hasn't cooled off up there. It's cold in the winter and warm in the summer. I think we have to take a good look at the insulation in the crawl space.

  3. If we could, we'd have 2 zone thermostats. It's beastly hot upstairs, and cold on the first floor. There simply is no way, under the current controls, to make both areas reasonably comfortable at the same time.