I was reading an issue of Popular Science (25th annual 'Best of What's New issue, page 7) when a Philips LED bulb ad caught my eye. I read in the top portion of the ad that using an 11W, 800 lumen Philips LED bulb could save you $134 annually over the cost of a standard 60W bulb. Annually is the key word here. Naturally, I had to do the math.
In the footnotes, they explain that the savings was calculated by using a cost basis of 11 cents per kWh as the electricity rate and an estimated life of 25,000 hours for the bulb. There are only 8760 hours in a year, and that's if you use the bulb 24 hours a day, 7 days a week. A kWh (kilowatt hour) is 1000 watt hours or in this case about 91 hours of continuous use for an 11 watt bulb.
In the second footnote they explain how they calculated the 22.8 year lifespan of the bulb. It's based on estimated usage of just 3 hours a day. If you accept that as an average use number, it would actually take you almost 19 years to realize that $134 in savings.
They didn't display a price for this particular bulb in this ad, but LED bulbs in general currently go for between $30 and $60 at Home Depot or Lowes, so you could recoup the cost of the bulb in electricity savings in between 4 and 8 years, assuming you stay in your current home for that long, or you take your light bulbs with you when you move.
Here's an even simpler way to look at it. If you can really save $134 annually per bulb using an 11 watt as opposed to a 60 watt bulb, that means you're currently paying about $165 per year, per light bulb in your home. If you have just 20 light bulbs, that's $3300 per year or $275 per month, just for light bulbs. That doesn't include your TV's, computers, radio's, hot water heater, appliances, etc. Does that sound right to you?
