CFL Light Bulbs - Electricity Analysis


Most of us believe that compact fluorescent light bulbs save electricity. As I looked for further ways to save electricity in our apartment (having exhausted all the obvious suggestions) I noticed that there were a number of non-standard size bulbs (twelve to be exact - "the dirty dozen") that had not been replaced.

We have two articles on this - Dirty Dozen arrested by Missouri Highway Patrol - explaining the types of bulbs we needed, and Incandescent vs. CFL - Electricity Analysis showing the actual electricity use for each set of light bulbs over a two day period.

The graph compares the electricity used for the two sets of light bulbs, each set being turned on in the same sequence, with 15 seconds between each light being turned on. Please see the notes at the end of this article for information on using CFL's in a bathroom, and our plan to replace them with LED's

X Axis - 15 second time intervals
Y Axis - Watts

Although I expected a savings, the results are quite dramatic when visualized. If it were not for the bathroom fan, which did not change, the new lights would have been saving more than 75% of the electricity of the old.

I do suggest you look at the right hand side of this graph and compare it to that of the left.

There is no trickery and the axis are the same. This is what a 75% electricity saving for a regular two bedroom apartment looks like when you replace the old incandescent bulbs, with the latest technology CFL bulbs.

I encourage you to look at our forum on Home Energy Lighting where we have articles on the history of CFL's, how to select a CFL - particularly regarding CFL disposal, Mercury, Light intensity, Light color and Buzzing.

Update: October 2010 - I have noticed that the T2 A19 CFL's, with frosted glass cover (looking like a regular bulb) do take a few minutes to reach the full 800 Lumens.

Update: November 2010 - I need to qualify my earlier thoughts. In most cases waiting for the CFL light bulb to reach its full intensity is not an issue. This is not working out for our bathroom - the delay is an issue!

Update: December 2011 - We have persevered, the bulbs are still working but the delay is getting longer as the bulbs age. They will soon be replaced - I hope to try LED's - stand by!

Update: March 2012 - We are working with LED Lighting Gallery to test the use of their A19 - 9W LED light bulbs - for our bathroom. We hope to reduce the energy footprint a further 35%, end the issue of waiting for the bulbs to reach full light intensity, and enjoy 11 years of useful life!


Open4Energy - Get Smart about Energy™

Interesting information!

Interesting information!

2 points to remember though are power factor (taking into account power generated at power station, not showing on meter, but payable of course anyway in the bills) typically halving the supposed CFL savings, and the heat factor of ordinary bulbs, especially in temperate climates after dark, in well insulated houses.

I run through ordinary light bulb and CFL savings comparisons from onwards, and heat factor at including governmental/institutional references.

Savings are not as great as supposed, and in my view one should simply choose the light one prefers, but of course if savings are a priority, and one realizes how and when best to use CFLs in such a case (not switching on-off for brief periods, using more in summertime, not using in cold or rarely used locations etc) then why not...

WOW your link is scary

WOW your link is very scary.. you could make a good horror film using that site.

I've been using CFL bulbs since 1979 when Philips first introduced them to the UK.

Had my first Mortgage on my first house was short of money these were the way to save money on Power.

In 2009 4 houses later I removed all my CFL bulbs to replace them with LED bulbs as there even cheaper to run.

What problems did I have.. in all those years. NONE!!.

Saving the cost of the bulbs easily even when they were $15 a bulb in 1979 they originally had a 5 year warranty.

In the UK now your power company gives you 4-5 CFL bulbs free of charge.
Supermarkets now have buy one get 3 free offers... so for £0.33p you get 4 CFL bulbs thats > $0:20 for 4 CFL bulbs.

I tended to prefer Ikea CFL bulbs as they make nice variety of bulbs including spot lamps.
They also have the full variety of fittings all the sizes of ES to the standard UK bayonet fitting.
ES = Edison screw not usual used in the UK but growing.

So do they last that long! Oh yes they last for years.

As for Power factor.. ?? What!! these devices are electronic with teeny tiny inductors.

Its a bit like some one saying to you that your headphones or HiFi/PC have speakers, affect the Power Factor of the electricity you use in your home.

If the above were true every single electronic device in your house would be affecting your power factor.

Why because virtually every single electronic device you have will have a high efficiency switch mode power supply. The inductors used in those high efficiency switch mode supplies are significantly bigger than those used in a CFL bulb.

Yes I havee been a penny pinching electronics engineer for quite a long time.
It is nice to see that my daughtes have followed my example.