As a user of both LEDs and CFLs I tend to prefer the LEDs on all counts except price. The turn-on time is usually much faster, there is no warmup time, and despite CFL reliability claims, LED demonstrate superior reliability. We use a lot of CFLs because they are so much less expensive than LEDs–even factoring in the lower reliability.

Ignoring price and reliability for the moment, the largest distinction for me between LED and CFL lamps is the turn-on and warmup time issues. The main goal of this light evaluation project was to start putting some solid numbers on turn-on time and warmup time, although I also measured some other parameters.

The following plot demonstrates the issues involved with two representative lamps.

LED lamps generally have a turn-on time about as fast as an incandescent, typically 100 to 200 msec, which most of us are accustomed to. For home lighting this turn-on time is not an issue. And when they do turn on they are immediately at or above 80% of the fully warmed up light output.

CFLs based on my test results have a much wider spread in turn-on time. Some CFLs approach the turn-on time of LEDs while others can take more than one second. This isn’t a long time but it is sometimes long enough to stop me when walking into a really dark closet at night.

More of an issue to me than the slow turn-on time of CFLs is the slow warm-up time. When I walk into my office and turn on the lights, the CFLs leave it uncomfortably dark for the good part of a minute. I size my lighting to the illumination I need. If I could get by with 40% of the light I would use fewer lamps to start with. The long warmup time of CFLs encourages me to leave the lights on all day, even when I leave the office for lunch. I’ve improved the situation somewhat by replacing one of my track light CFLs with an LED floodlight that illuminates the desk where I most commonly work. This gives me light where I usually want it immediately. Within a minute the rest of my office is about up to full illumination.

In the plot above I’ve used 80% of maximum lumens as the reference light output for determining warmup time. So the CFL in used for this plot took a total of 25 seconds to reach 80% of the maximum lumens. This performance isn’t average, you are looking at the fastest warming up  CFL of all the CFLs I tested. One CFL took 87 seconds to reach 80% of maximum lumens. You can see more details in the test results or view all the plots for the lamps I’ve tested in the individual lamp test results.