jumpy jumpy vitamins

The quick version of this post:

energy efficiency saves you money, stupidhead.

The long version:

Look. We all know gas prices are ridiculous, and that market forces are going to be scrambling to catch up for a while, and that there are environmental reasons to be energy-efficient, blah blah blah. Much of our collective problem, is that it’s apparently pretty easy to forget about energy efficiency when energy prices are low. So let’s crunch some numbers.

To calculate the per-hour cost of running a particular electrical item — a light, a refrigerator, a TV, whatever —

• Determine its electrical usage in watts. Some items, such as light bulbs, list this outright; those are easy. Other items, such as computers or refrigerators, list voltage and amperage; these use differing amounts of electricity depending on what they’re doing, but you can figure the theoretical maximum wattage by multiplying volts by amperes.
• Divide usage in watts by one thousand to get usage in kilowatts. (Americans: “kilo-” means “one thousand”. It’s that icky metric stuff, I know, but stick with me.)
• Find your local utility’s rate per kilowatt-hour. It should be on their Web site, though you may have to wade through several types of rate. (Right now, I would look at my utility’s summer residential rate, which comes to 7.92 cents per kilowatt-hour [PDF].)
• Multiply the per-kilowatt-hour rate by the usage in kilowatts. Your result is the per-hour cost to operate this item.

As an example, let’s discuss lighting in my kitchen, where there are five bulbs in a ceiling fan. On an average day, we’re in there using those lights for about three hours total; those lights are typically off when they aren’t in use. Throw in a thirty-day average billing cycle and here’s how much it used to cost to light that room, before we swapped incandescent bulbs for CFLs:

• Five bulbs, 60W per bulb = 300W total to use
• Three hours of usage per day, 300W while in use = 0.9kWh per day
• Thirty days in a billing cycle, 0.9kWh per day = 27kWh per cycle
• 27 kWh per cycle at the rates above ~= $2.14 per month in summer

Using 14W CFL bulbs in the same pattern providing the same amount of light:

• Five bulbs, 14W per bulb = 70W total to use
• Three hours of usage per day, 70W while in use = 0.21kWh per day
• Thirty days in a cycle, 0.21kWh per day = 6.3kWh per cycle
• 6.3kWh per cycle at the rates above ~= $0.50 per month in summer

And that’s just one fixture in one room, at rates that are relatively low for U.S. urban centers. The savings are even more pronounced at higher rates: in Juneau, where rates recently hit 56 cents/kWh, that one light fixture would have cost $15.12 per month with incandescents (ouch!), but only $3.53 per month with CFLs (much less ouch).

While it will cost around $10 to put five CFLs in that fixture (vs. $2.50 for five new incandescents, using multi-pack prices from a Home Depot near me), the extra up-front cost will be recaptured after about 4 months of average use at my house. It’s also worth noting that CFLs last about five times longer than incandescents, so you can often come out ahead just on the cost of the bulbs themselves.

(Aside: What’s the heat source on the original Easy-Bake Oven? An incandescent light bulb! “Incandescent” means “glowing hot”, after all. Think about that while your air conditioner runs up your utility bills.)

[And yes, LEDs are considerably more energy-efficient and longer-lasting than CFLs. Unfortunately, their up-front cost is appalling at the moment ($60 for a single bulb?!), so until prices come way, way, way, way, way down I don't see LEDs replacing CFLs.]

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