A lot of our customers like to touch and handle our bulbs a lot – at times when they otherwise wouldn't for standard incandescent or CFL bulbs (don't worry, we do the same too). So one of the popular questions we get is, “wow, your lightbulbs are hot. Is that okay?” Our VP of Engineering, Marc Alexander, takes a look at this question. How hot are LED light bulbs? Hot! Hot to the touch, but not nearly as hot as Incandescent, Halogen and CFL bulbs are. LED light bulbs are one of the latest and most efficient lighting technologies. High powered lighting LEDs generate light at a much lower running temperatures than the hot filament used in previous generation bulbs. The hottest outside surface of an LED light bulb is often half the temperature of an equivalent brightness Incandescent or Halogen bulb, and around 20% cooler than CFL bulbs. Should I touch my LED light bulb when it's on? LED light bulbs should be handled by the diffuser – the plastic dome that the light shines out of. When it's lit or hot, don't touch or handle LED light bulbs by the heat sink. Heat sinks on LED light bulbs are designed to get hot, drawing the heat out of the LEDs and transferring the heat into the air. It's the hottest part of the bulb, and for good reason – the heat sink is designed to be the hottest part, while keeping the LED power supply and electronics as cool as possible. Okay, but how 'hot' is hot? In development and testing, we found that the heatsink of a fully lit LED bulb was around 60°C to 100°C (140°F to 212°F) depending on the make and model of the LED bulb, room temperature and airflow. Here's a thermal camera image analysis including some representative top brand-name samples of LED light bulbs – purchased new last week from the supermarket and hardware store. Brighter yellow is a higher temperature.
From left to right: 9W LED. Compact LED bulb (output: 600 lumens) 9W LED. Compact LED bulb (output: unspecified, looks 600 lumens) 13W LED. A19 size bulb (output: 1055 lumens) LIFX A21. A21 size bulb, full-color range, set to maximum power white (output: > 1000 lumens) The two 9W compact LED bulbs are the hottest! Though the compact bulbs are lower power and lower light output, there is very little heat sink area and no airflow management. The power supply electronics are sitting directly inside the sealed 86°C 186°F heat sink. The 13W LED A19 bulb at third is a little bit cooler. It's 30% brighter than the two compact bulbs, but it has a larger heat sink area to work with and get the LED heat out into the room air. The LIFX A21 bulb is the coolest. It has an airflow management design which uses convection airflow through the body, flowing both inside and outside the heat sink. The power supply and electronics sections are kept as cool as possible in this next generation bulb. In even hotter room temperatures than the warm 28°C 82°F used in this test, or in semi-sealed enclosures, the LIFX A21 bulb keeps the lowest possible temperatures for the electronics and heat sink system, especially compared to current model LED light bulbs as tested in sockets 1-3. Why does it feel so hot when I touch the heat sink? Any object above 50°C 122°F will quickly feel very hot when touching it with your fingers! You will reflexively pull away. It's a heat sink, so always remember that it is supposed to be hot. Your fingertips and pain sensors are automatically protecting themselves from the temperature where the proteins in your skin will start cooking. This cooking is also called 'protein denaturing or unfolding'. This cooking starts from around 57°C 134°F and up. It's a reflex response to remove your body parts quickly from anything hotter than 50°C 122°F, and get the message that something is 'way too hot'. Could I burn my fingers? If you don't reflexively remove your fingers within a few seconds of anything hotter than around 55°C 131°F, yes – you'll burn your fingers. Don't touch the hot parts of any light bulb. This includes nearly all lighting technologies including the new generation of LED light bulbs with efficient, lower temperature heat sinks. What temperature is ok for LED light bulb electronics? We can't speak for all LED light bulbs, but good quality designs use power supply and driver components rated for 125°C 257°F. Note that this is the internal electronics temperature, different to the outside heat sink temperature. Done properly, a bulb design can keep the electronics temperature at least 10°C to 30°C lower (18°F to 54°F lower) than the heat sink temperature. So an LED bulb with a heat sink temperature of even 90°C 194°F could comfortably have an electronics temperature of 60°C to 80°C (140°F to 176°F), both well under the temperature rating for the electronics components. Does the light bulb position matter? Yes. Light bulbs positioned straight up or straight down will generally run cooler than sideways. The hot convection air flow flows past more of the bulb length, so it cools a bit more effectively. Sideways is still acceptable though and tested to be within normal operating temperature ranges. In testing, the heat sink on a sideways mounted LIFX A21 bulb in a ceiling mounted semi-enclosed fitting was around 85°C 185°F, but more importantly, the power supply electronics temperature measured 75°C 167°F, and the driver control electronics was kept at 53°C 127°F, a good advantage. Room temperature was 28°C 82°F for this and the CFL heat comparison. For comparison, a similar lumen output CFL lamp in the same test was running a glass temperature of 120°C 248°F and electronics temperature of 85°C 185°F. 32°C higher than the LED based system. What safety testing is done? Light bulbs for the USA and all customers worldwide have been through extensive independent laboratory testing and certification processes. This includes UL safety testing for lighting products, which includes checking the high temperature materials and components used in the light bulb's design and production, and a sealed 'heat box' test. We're serious about our technology, so the LIFX A21 bulb has an additional safety feature beyond what's required to pass UL and other certification and safety tests: The power supply is self protected and will turn itself off at an internal temperature of 105 to 115°C. It's not possible to trip this protection in normal operation across the extended temperature range, but we put this protection in the system as an extra feature. How hot are other light bulbs that aren't using LEDs? Smoking hot! Don't even consider touching other kinds of light bulbs. Incandescent and Halogen bulbs shown in this test were as hot as 181°C 357°F, and sections of the glass on a CFL bulb were as hot as 131°C 267°F.
Though you can safely handle most LED light bulbs from the plastic diffuser without getting burnt, do not under any circumstances touch an incandescent or halogen bulb. And as detailed here, although the LIFX A21 bulb design runs cooler and safer to touch than this representative sample of current model LED light bulbs, any heat sink on an LED light bulb shouldn't be touched. Even if the bulb looks good in its fitting and it's tempting to touch and handle it!