# Does three 20W fluorescent light bulbs equal one 60W bulb? **URL:** \ **Category:** Factual Questions\ **Created:** [May 23, 2003, 7:08pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083 "2003-05-23T19:08:34Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![InLikeFlynn](https://avatars.discourse-cdn.com/v4/letter/i/f19dbf/32.png) [@InLikeFlynn](https://boards.straightdope.com/u/InLikeFlynn)\ **Post date:** [May 23, 2003, 7:08pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/1 "2003-05-23T19:08:34Z")
I know that they would use the same amount of energy to power so they would have to be equal (right?) but, is there any difference in their respective wavelengths? This problem arose from trying to light up a fish tank with enough intensity to sustain delicate sea anemones! Would both instances penetrate the water to the same depth? 😕 ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 23, 2003, 7:20pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/2 "2003-05-23T19:20:07Z")
One 20 W fluorescent bulb emits about the same light energy as a 60 W incandescent bulb. Flourescents are much more energy-efficient than incandescents are. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 23, 2003, 7:25pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/3 "2003-05-23T19:25:35Z")
Oh, and just to clarify, wavelength and intensity are not the same thing. Both kinds of bulb emit many different wavelengths, but each in a different kind of distribution. Wavelength equates to the color of the light, while intensity refers to the amount of light. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [May 23, 2003, 7:39pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/4 "2003-05-23T19:39:27Z")
Yes, I believe you will get pretty much the same yield in lumens/watt if the tubes are of the same type. Q.E.D., I think you misunderstood the question. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [May 23, 2003, 7:55pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/5 "2003-05-23T19:55:45Z")
One 20-watt fluorescent: 1275 lumens. One 60-watt soft white bulb: 860 lumens. One 60-watt standard clear bulb: 900 lumens. Question is, is the OP asking about the output of three 20-watt fluorescents compared with one 60-watt fluorescent or compared with one 60-watt incandescent? ---
**Author:** ![frithrah](https://avatars.discourse-cdn.com/v4/letter/f/ad7895/32.png) [@frithrah](https://boards.straightdope.com/u/frithrah)\ **Post date:** [May 23, 2003, 8:05pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/6 "2003-05-23T20:05:03Z")
Answering a question such as this may violate any number of new laws under the rule of Ashcroft, or if not, probably will very soon; just ask Ed Rosenthal whom the pope absent-mindedly neglected to canonize last week. Anyway, Incandescent bulbs give off a great deal more of their energy as heat than do fluorescents. If you were asking for this comparison, then yes. Fluorescents also take very little energy to start, whereas incandescents, as I recall, electrically consume about a half hour’s worth of burn time just to get the juice flowing through the filament when you throw the switch. If you are comparing your propsed wattages with both bulb styles being flourescent, it gets a bit trickier. The ballasts also consume energy that is dissapated as heat. If each 20 watt has it’s own as compared to one 60 watt ballast, they may in fact collectively perform less efficiently. Generally though, I would say the difference would be fairly negligible and you could get more uniform lumen distribution from the 3 individual bulbs. ---
**Author:** ![InLikeFlynn](https://avatars.discourse-cdn.com/v4/letter/i/f19dbf/32.png) [@InLikeFlynn](https://boards.straightdope.com/u/InLikeFlynn)\ **Post date:** [May 23, 2003, 9:09pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/7 "2003-05-23T21:09:19Z")
Now I’m even more confused!! No, I’m not trying to compare incandescent with fluorescent. I am trying to compare apples with apples just different sizes. Does One 60 Watt fluorescent = Three 20 Watt fluorescent bulbs in intensity? Will they both penetrate water to the same depth? Are they the same exact thing? If not, then what is the difference? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 23, 2003, 9:15pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/8 "2003-05-23T21:15:31Z")
Oh I see now. Yes, as **sailor** said, and I would have said if your OP had been slightly clearer, three 20 W bulbs will be approximately the same intensity as one 60 W bulb. ---
**Author:** ![pestie](https://avatars.discourse-cdn.com/v4/letter/p/e5b9ba/32.png) [@pestie](https://boards.straightdope.com/u/pestie)\ **Post date:** [May 23, 2003, 9:26pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/9 "2003-05-23T21:26:22Z")
The easiest way to be reasonably sure is to look at the lumens of the bulbs. If each 20-watt bulb puts out 1200 lumens and the 60-watt puts out 3600, then yes, they’re equivalent. If not, then no. ---
**Author:** ![drhess](https://avatars.discourse-cdn.com/v4/letter/d/94ad74/32.png) [@drhess](https://boards.straightdope.com/u/drhess)\ **Post date:** [May 23, 2003, 9:31pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/10 "2003-05-23T21:31:22Z")
I don’t think lumens and watts are directly related in this case, as the bulb design (finish, etc.) has an impact. As others said, look at the lumens on the box, not the wattage, and add the lumens up! Right? ---
**Author:** ![InLikeFlynn](https://avatars.discourse-cdn.com/v4/letter/i/f19dbf/32.png) [@InLikeFlynn](https://boards.straightdope.com/u/InLikeFlynn)\ **Post date:** [May 23, 2003, 10:36pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/11 "2003-05-23T22:36:57Z")
I’ll look into the lumen factor, thanks! What is a lumen? Is it somthing related to candle power? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 23, 2003, 10:38pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/12 "2003-05-23T22:38:36Z")
1 lumen = 1 standard candle at 1 meter away. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 23, 2003, 10:41pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/13 "2003-05-23T22:41:26Z")
Oops…memory kicked in too late. Make that one foot-candle illuminating and area of one square foot. ---
**Author:** ![manhattan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/manhattan/32/7_2.png) [@manhattan](https://boards.straightdope.com/u/manhattan)\ **Post date:** [May 23, 2003, 11:09pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/14 "2003-05-23T23:09:43Z")
> [@](#): > > \*Originally posted by frithrah \* > \*\*Answering a question such as this may violate any number of new laws under the rule of Ashcroft, or if not, probably will very > soon; \*\* I eagerly await your factual citation to this assertion. I mean, since you made it in GQ, it is factual, yes? You can email it to me if you prefer not to look like an idiot in public. ---
**Author:** ![minor7flat5](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/minor7flat5/32/258_2.png) [@minor7flat5](https://boards.straightdope.com/u/minor7flat5)\ **Post date:** [May 24, 2003, 1:22am UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/15 "2003-05-24T01:22:58Z")
I’m totally ignorant on this subject, so humor me… So, as I understand the comments here, lumens are perfectly additive always (for same frequency). Is this correct? How about perceived brightness… If I double the lumens does it appear twice as bright, or is it a logrithmic kind of thing (like dB)? ---
**Author:** ![InLikeFlynn](https://avatars.discourse-cdn.com/v4/letter/i/f19dbf/32.png) [@InLikeFlynn](https://boards.straightdope.com/u/InLikeFlynn)\ **Post date:** [May 24, 2003, 10:40pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/16 "2003-05-24T22:40:23Z")
I now know what a lumen is. Great but that only rephrases my question. Does TWO fluorescent 1275 lumen bulbs = ONE 2550 lumens bulb? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [May 24, 2003, 10:48pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/17 "2003-05-24T22:48:00Z")
> [@](#): > > \*Originally posted by InLikeFlynn \* > \*\*I now know what a lumen is. Great but that only rephrases my question. > > Does TWO fluorescent 1275 lumen bulbs = ONE 2550 lumens bulb? > \*\* For your purposes, yes. ---
**Author:** ![x-ray\_vision](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/x-ray_vision/32/351_2.png) [@x-ray\_vision](https://boards.straightdope.com/u/x-ray_vision)\ **Post date:** [May 24, 2003, 10:49pm UTC](https://boards.straightdope.com/t/does-three-20w-fluorescent-light-bulbs-equal-one-60w-bulb/177083/18 "2003-05-24T22:49:17Z")
Yes, two bulbs giving out 1275 lumens a piece would equal one bulb giving out 2550 lumens, but that’s changing the question, not rephrasing it. Watts are a differeny story.