# Flourescent replacement bulbs require warm-up? **URL:** \ **Category:** Factual Questions\ **Created:** [March 2, 2006, 3:12am UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717 "2006-03-02T03:12:16Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [March 2, 2006, 3:12am UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/1 "2006-03-02T03:12:16Z")
I replaced a couple of indoor floods with an energy-saving version that uses fluorescent tubes (you can see the spiral inside the bulb). But they start out dim and need several minutes to warm up to full operating intensity. These were a bargain at Costco but I think they’re just junk. Is that normal? Other fluorescent replacement bulbs I have bought don’t do this. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [March 2, 2006, 3:20am UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/2 "2006-03-02T03:20:08Z")
It varies by Bulb and Manufacturor. SOme bulbs come up quick and some come up slow. I must have the same brand you do, my indoor Floods are also very slow to warm up. Most of the CFs are fairly quick. Jim ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [March 2, 2006, 3:40am UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/3 "2006-03-02T03:40:38Z")
Some compact fluorescent lamps just do this. Technically I think all fluorescent lamps do this (start out dimmer than rated and work up to full brightness) but most turn on bright enough and close the gap fast enough that it isn’t an issue. Some on the other hand seem to take minutes and are awful. Unfortunatley I know of no way around this. Not surprisingly manufacturers do not bother telling you on the package that their light bulb takes forever to turn on fully. Best I can suggest is to test the bulb in the store if possible. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [March 2, 2006, 3:41am UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/4 "2006-03-02T03:41:05Z")
I second **What Exit?'s** statement. Some of the "economy’ units do take some time to get going. It’s not too much of an issue if it’s a bulb that’s on for a long period, but they are not suitable for locations where you want full brightness at turn on. I had one in a bedside lamp and it worked out well because it wasn’t blindingly bright when you switched the lamp on at 3 AM. Costco has a good return policy, take them back and get your money back. ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [March 2, 2006, 4:05am UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/5 "2006-03-02T04:05:02Z")
Just for the heck of it, what is the ambient temperature of the room where the bulbs are located? Cooler rooms, like 3 season porches or unheated basements during the winter can delay CF lamps from reaching full brilliance for a few minutes. ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [March 2, 2006, 4:30am UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/6 "2006-03-02T04:30:55Z")
Also, if the lamp is on a dimmer switch, that will mess with it. CF’s don’t like dimmers at all. ---
**Author:** ![CookingWithGas](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cookingwithgas/32/485_2.png) [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)\ **Post date:** [March 2, 2006, 2:32pm UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/7 "2006-03-02T14:32:50Z")
> [@danceswithcats](#): > > Just for the heck of it, what is the ambient temperature of the room where the bulbs are located? Cooler rooms, like 3 season porches or unheated basements during the winter can delay CF lamps from reaching full brilliance for a few minutes. One’s in the master bathroom, 69[sup]o[/sup]F in the winter. The other is in the garage, so it can get cold but usually not much below 40. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [March 2, 2006, 2:41pm UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/8 "2006-03-02T14:41:02Z")
> [@CookingWithGas](#): > > One’s in the master bathroom, 69[sup]o[/sup]F in the winter. The other is in the garage, so it can get cold but usually not much below 40. The 2 in my garage work great. Don’t use them in a Garage door opener however. As I said, not all bulbs are equal. Jim ---
**Author:** ![control-z](https://avatars.discourse-cdn.com/v4/letter/c/eada6e/32.png) [@control-z](https://boards.straightdope.com/u/control-z)\ **Post date:** [March 2, 2006, 4:31pm UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/9 "2006-03-02T16:31:25Z")
Yeah I got some cheap(ish) flourescent bulbs, and while they do come on without flickering like older ones did, they take 30 sec or so to get fully bright. Annoying but I can live with it. If they get many returns I bet things will change. ---
**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:** [March 2, 2006, 4:41pm UTC](https://boards.straightdope.com/t/flourescent-replacement-bulbs-require-warm-up/346717/10 "2006-03-02T16:41:21Z")
> [@AskNott](#): > > Also, if the lamp is on a dimmer switch, that will mess with it. CF’s don’t like dimmers at all. That’s true for standard CF bulbs, but there are now dimmable CF bulbs that will work properly with a dimmer. Naturally, these cost more.