Halogen bulbs are incandescent bulbs. Halogen bulbs, however, are filled with a special gas that actually rebuilds the filament and provides longer average lifespan than normal incandescent bulbs. They come in different shapes and sizes for various different uses. The PAR series of halogen bulbs are flood shaped with heavy, thick glass that is common to many medium to large sized halogen bulbs. PAR stands for parabolic aluminized reflector. These types of bulbs will provide you with a higher light output, a more white-colored light (a higher color temperature - approximately 3000K), and longer life than normal R or BR reflectors.
The PAR36 bulbs are not commonly used compared to the other bulbs in the PAR lamp family. You can tell what kind of PAR lamp you have by measuring the distance across the widest point of the bulb. The number after 'PAR' represents the number of eighths of an inch the bulb diameter is. Therefore, PAR36 lamps are 4 1/2 inches across.
PAR36 lamps are available from Sylvania, Philips, Wagner, and GE. They have screw terminal & spade connector bases. This base type is like none other and is not interchangeable with other types of bulbs. In order to attach this bulb to the fixture, a screwdriver is needed. Once the screws are loosened, the wire connections from the fixture are hooked onto the screws, which are then tightened in order to secure the wire connection.
The Sylvania brand for all PAR lamps is Capsylite. The GE brand for all PAR lamps is Edison. The Philips brand for all PAR lamps is Halogena. You can get the bulb in VNSP (very narrow spot), NSP (narrrow spot), and WFL (wide flood) beam spreads. The VNSP is about 5 degrees, the NSP is about 13 degrees, and the WFL is about 32 degrees. If you want to light up a large area, then use the WFL. If you want to focus the light into a small area, try the VNSP or the NSP.
These bulbs can be found in various wattages and voltages. By far, the most common is 36 watts and 12 volts. The description of the bulb from major manufactures would be 36PAR36. The bulbs are used in automotive applications as well as specialized industrial and commercial applications. It is truly rare to find a PAR36 bulb used in a residence.
These bulbs are short, yet wide. They give off a good quality light with a high CRI (100) and the previously mentioned Kelvin temperature of about 3000K. The common 36 watt 12 volt models typically last an average of 4000 hours and they provide 700 lumens of light output. They contain a C-8 filament.