Switching to Flourescent Light Bulbs & Savings Calculations

I just finished replacing all of my 60-watt regular incandescent light bulbs in my place with the equivalent 11-watt fluorescent ones. I had been waiting for each to burn out one-by-one, but after finding a bunch on sale at Ikea I just decided to do them all. After crunching some numbers, it seems like that would be the best decision anyways. Here are my calculations:

10 bulbs x ~4 hours a day x 1 year = 14,600 hours of lighting.

Cost of electricity:
60 watts x 14,600 = 876 kW-hr vs. 11 watts x 14,600 = 161 kW-hr.
Savings: 515 kW-hr x 0.083 cents/kW-hr (taken from recent bill) = $43/year.

Cost of bulbs:
At a lifespan of 1,000 hours for regular bulbs, I’ll need 14.6 new bulbs/year x $0.50 per bulb = $7.30/year
At a lifespan of 10,000 hours for fluorescents, I’ll need 1.46 bulbs/year x $2.50 per bulb = $3.65/year (exactly half, whoa.)
Savings: $3.65/year

Cost of 10 new bulbs: $25. Total savings from switching: ~$47/year.

Not too shabby, I’ll make back my investment in little over half a year. I’m also pretty impressed with the bulbs. My older fluorescents are the spiral-type, and sometimes take a couple seconds to reach full brightness. These new ones are “linear” and more compact, and light up almost instantaneously. Too bad this is basically the extent of my handy-man capabilities.


  1. We’re in the process of switching out our incandescent bulbs also, but we’re installing the spiral-type fluorescent bulbs. Acquired ‘em at Sam’s, where they were significantly cheaper than other places.

    If they last as long as advertised (guaranteed 5 years), I’ll be a happy camper. (I get real tired, real quick, of replacing the same bulbs over and over in our kitchen.) The energy cost savings are gravy.

  2. I am a mechanical engineer and I must say there is something wrong with your calculations. You forgot to figure in the fact that incandescent bulbs give off more heat then the energy efficient bulbs. In the summer months you pay good money to power your AC to get rid of this extra heat. So in the summer you actually save more since the efficient bulbs give off less heat. In the winter the exact oppisite happens, the bulbs produce less heat, but you want heat in you house. So in the winter your electic bill will go down, but your heating bill will go UP! The actual calculations for such an engineering analysis is beyond the scope of this input. However when you do the calculations (these depend on the efficency of the devices in your home) you should find the cost of heating your home 1 BTU by natural gas is about 1/2 as much as heating it by electricity. So, you still save in the winter just not nearly as much as in the summer. As an engineer I have found certain building will loose money by switching to energy efficient lighting. So don’t assume you will always save by switching to more energy efficient devices.

  3. I have been switching to compact flourescent bulbs in my home for years now and am suprised to find that they don’t last as long as they say. I’m getting months out of some, not years. I do tend to get them at Sam’s where they are definitely cheaper than most retailers. Maybe the old adage “You get what you pay for” is true in this case.

  4. I have to agree with Todd to some extent. I’ve noticed that the bulbs are yellowing and dimming in comparison to newer bulbs. I made this change of bulbs in my house and a 10-room house (with many common living areas). I paid the bulbs off after only 3 months of electricity savings! In the 10-room house, it cut the electrical bill down by about $200 per month immediately (from about $800 to $600). The bulbs paid themselves off in just a couple of months too. I haven’t changed too many after nearly 2 years, there.

    If you can handle the lighting change, then I’d go for it personally. I guess some women don’t like it when they put on their make-up. The comment I have from a lady is that if she put on her make-up in that lighting that she’d look like she was putting it on for the red light district when she was done! I got a good chuckle out of that and allowed her the incandescent bulbs she wanted in the bathroom.

  5. We tried making the switch, but our (rented) house had older wiring. The flourescent bulbs burned out within a year; we replaced them twice at Home Depot. Finally, we gave up. Turns out it’s more cost effective for us to stay with incandescent bulbs.

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