Valerie writes: “Someone in our family recently suggested that compact fluourescents weren’t worth it due to their high initial cost compared to incandescent light bulbs. We’ve switched all our lights to CFL, so my husband looked into the actual costs. I thought you might like the results” In this guest post, she lays out the numbers.

It makes good economic sense to switch from Incandescents to compact fluorescents (CFLs) — it’s not just a bunch of hype. Let me use our very conservative electrical bill to demonstrate how making the switch can save you money.

Our total consumption for July and August was 1195 kilowatt hours (kWh). This equates to 19 kWh/Day — far below the U.S. average of 29 kWh/Day. Part of this low consumption is because we’ve already replaced most of our incandescents with CFLs. But let’s say we haven’t, and assume that our electrical bill with incandescents is the same as it is now.

According to the American Lighting Association, lights account for 25 percent of a homeowner’s electric bill. But let’s assume they’re exaggerating, and put this to 20 percent.

Since we don’t use a lot of electricity in our household, 98% of all our electricity is charged at the lowest rate: \$0.053 per kWh. About two percent is charged at \$0.062 per kWh. For simplicity’s sake, we’ll just assume we get all of our electricity at the lowest rate.

Here’s the math:

• 20% of our total electricity consumption for 2 months: 1195 * 20% = 229 kWh for lighting
• 229 kWh charged at \$0.053: 229 * \$0.053 = \$12.67 for lighting
• In our area, we also have the delivery, regulatory and debt retirement charges totaling \$0.038 per kWh: 229 * \$0.038 = \$7.74 for lighting

If instead of using 60-watt incandescent bulbs we use 13-watt CFLs, we’ll be using 21.67% as much energy (13 watts divided by 60 watts is 0.2167). Applying this fraction to the cost of lighting, we now pay \$2.75/month instead of \$12.67, which saves us \$9.92. Applying the other miscellaneous charges, we now pay \$1.68 instead of \$7.74, saving us \$6.06. Using these numbers, we’re saving \$15.98 per billing period.

It’s true that CFLs cost a lot more than incandescents, but their prices are dropping every day. Also, you can always get them on sale and/or use special coupons to get discounts. We replaced most of our incandescents in our house for around \$85. (J.D.’s note: When we bought this house, we had a free home energy audit from Energy Trust of Oregon. They gave us six or seven CFLs for free!)

Even if, for the sake of illustration, we put the cost of incandescents at \$0, CFLs will pay themselves off in just a few months. It’s been over a year now since we installed ours, and none have burned out. CFLs are rated for about seven years, which means that for the next six years, they’re saving us money. Even after stacking the cards against us, with the low electricity bill, paying the lowest rate, and assuming incandescents cost nothing, CFLs make sense.

Given that the bulbs should last seven years, we can expect to save at least \$575.28, which isn’t bad for a couple of hours of work.

Michael Bluejay has an extensive page describing how to save electricity on lighting. Also, I sometimes see people worry at other sites that CFLs are not safe. Turns out this is mostly an urban myth.) Photo courtesy David Hobby of Strobist.

Addendum: One commenter pointed to this video that explains CFLs in plain English. Though CFLs contain less only 1% of the mercury found in the average home thermometer, they must be disposed of safely. For the best information about how to do this, contact your local solid waste department. You can take CFLs to any IKEA store to dispose of them. In the U.S., you can learn more about disposing CFLs at the EPA’s bulb-recycling web site.