A21 vs A19 LED Light Bulbs
If you’ve ever searched for a 100-watt or 125-watt equal household LED light bulb, you’ve probably noticed a peculiar phenomenon: the standard A19 shape is often replaced with a slightly larger A21 shape. This is because bulb names like A19 and A21 are actually describing their shape through a letter code (A) and their diameters in eighths of an inch. A typical A19 is 2.375 inches in diameter (19/8 = 2.375) and 4.13 inches in height, while an A21 is 2.625 inches in diameter (21/8 = 2.625) and about 5 inches in height. Although the size difference is negligible in most applications, many buyers have been wanting to know why higher-wattage household LED bulbs are made in a larger size.
The “A” shape was one of the first light bulb designs, and it remains popular in homes to this day. Save for the slightly larger bulb and longer neck, the A21 looks just like an A19, and it is intended for many of the same fixtures and purposes. A-shape bulbs usually have a standard medium base that screws into sockets made for all kinds of residential light fixtures, though they are most common in table lamps and ceiling fans. These sorts of fixtures are often paired with 40 to 60 watt bulbs that produce an average of 450 to 800 lumens. However, some homeowners would like these light fixtures to produce brighter light, which traditionally would mean using incandescent bulbs that consume 100 watts or more. As you can imagine, this is problematic for the energy-efficient minded.
To mitigate this high power consumption, LED manufacturers have been trying to create energy-efficient solutions with 100-watt equal (and above) A-shape LEDs. Unfortunately, pesky heat issues can occur when trying to produce so much light with an LED light bulb. Higher-lumen LEDs are often made in an A21 shape (and not an A19 shape) because the increased size helps manufacturers get around the heat issues by providing a larger surface area for heat to escape from, thus protecting the sensitive internal electronics. While making 100-watt equal LEDs in an A19 shape is possible (some manufacturers even go through great pains to make them) 100-watt equal A21 bulbs are a lot less complicated to produce, and they are helping speed along the development of higher-lumen, energy-efficient residential bulbs.
As we’ve said earlier, the size of the A21 bulb will not make a difference most of the time, but it may in some fixtures. Before purchasing an A21 bulb, make sure your fixture will be able to accommodate the larger measurements!