Fluorescent bulb warm-up time

Why do CFLs need a warm-up period but tubes come right on?

Depends on the quality of the bulb/starter etc.

The newest, higher-priced CFL’s advertise ‘instant on’. Even regular new ones are pretty fast, compared to old ones. (I have one that’s been in my bathroom for several years now; it has quite a delay before it come fully on. Annoying. And the damn thing will probably last for years more before it ever burns out!)

And the 4-foot or 8-foot tubes used to have this same problem, years ago. But they have improved so much that it’s pretty unnoticeable now, except for ones outdoors in the cold.

Depends on what the bulb is made out of. The covered ones are more common these days, and these run hotter to be more efficient and to give a better light output. They also use a different type of mercury amalgam that prevents the bulb from overheating. The use of these different materials is what makes the bulb require such a long warm-up time. Because they run hotter, these types of bulbs also don’t last as long on average.

I use the older, slower acting ones in areas where I don’t need instant light. My kitchen early in the morning for example. I know where the coffee maker and the chairs and tables are. While slowly prying my eyes open, only enough illumination is needed to see if they have moved during the night. I’m not that interested in seeing the insects, dwarfs, and demons scuttling off to their hiding places. My bathroom near the medicine cabinet has instant on bulbs. Pain medication, bandages, tourniquets, etc… are a high priority and I’m probably wide awake at that point anyway.

Depends what you mean by “warm up time.”

For many bulbs there is a second or two delay between when the bulb is switched on and when it starts producing light.

There is another “warm up time” between when the bulb starts to produce light and it reaches its full brightess after a minute or two.

tubes can brighten over a minute time of turning on. it will depend on that individual bulb type and its condition.

both the tubes and CFL need to be at a certain temperature to start well.

In my experience, the reverse is the case.

I still have an ancient circular bulb in one lamp. It takes forever, but most of the CFL’s it is a second or less.

I have 2 lamps where the shade clips over the bulb. The newest CFL’s are just enough fatter in the middle I can now use them with those shades.

I bought two packages of GE CFLs. Both the same model number but slightly different packaging. One pair was instant on-full brightness right away. The other pair took a minute to get to full brightness.

To say YMMV with CFLs is an understatement.

Many products do. I’ve had incandescent bulbs that lasted less than half as long as another bulb from the same package.

And for lunch I had a cup of yogurt that I swear was 25% empty compared to the one I had at breakfast, same brand, same flavor, bought at the same time.