This is another article in a series dedicated to helping you create a home with beautiful lighting by choosing the best light bulbs. Recessed lights can be a little complicated, but once you've got the basics down, it's smooth sailing!
The first thing you'll need to do is determine which light bulb size your recessed light fixture takes. Here's what you'll see among recessed lighting options: BR30, MR11, MR16, PAR16, PAR20, PAR30, PAR38, R20, R30, R40.
Wow. Let's break that down a little:
The number following the letters in a recessed light bulb indicates size: it's the diameter of the light bulb in eighths of an inch. So, a BR30 is 30/8 inches, or three and 3/4 inches. An MR11 is 11/8 inches. So, you can swap out a PAR30 for an R30 or a BR30 - they are all the same size.
The PAR denotes the light bulb has a parabolic aluminized reflector on its inside, directing light out. That PAR coating maximizes the light output that you'll get from the light bulb. If brightness is your #1 priority in a recessed light, choose a PAR lamp in the appropriate size. The majority of PAR lamps are available in a flood beam spread, but spot beam PAR lamps are also out there. Many PAR lamps are approved for use in wet locations.
The MR indicates the light bulb has a multifaceted reflector on its inside. The facets help gather light from the filament to create a very concentrated light beam. MR lamps are primarily available in smaller sizes - they are all about beam control, which is typically desirable for a narrower light beam. You can choose your beam spread (i.e., narrow flood, flood, spotlight) for many MR lamps.
Moving on to BR: Want to take a guess on what it stands for? This is another reflector lamp to maximize brightness, but this time, the light bulb itself has a bulged shape to direct light out. One disadvantage of the BR lamp is that it's a little longer than the PAR and MR, which means it tends to sit lower in the recessed fixture - and perhaps, protrude from the bottom of the recessed light fixture.
Finally, the simple R. As you might assume, it stands for reflector in this case. There is a mirrored coating on the back of the light bulb to improve light output.
Now that we have those light bulb names deciphered, you should know that they are available in an array of light sources, including incandescent, halogen, compact fluorescent, cold cathode fluorescent, and LED. Halogen is probably the most popular of the bunch for recessed light fixtures. It renders colors very well, it's affordable, and it gives you a lot of light output.
If you're looking for efficiency, though, halogen is not your target. LED has a higher price point, but it also gives you a longer lifetime and lower energy use!
CFLs and CCFLs are also viable energy efficient options, but remember you should avoid the CFL if the gradual start-up drives you crazy - or if you plan to turn the lights on and off frequently. (You'll lower the lifetime of a CFL if you use it in less than 15 minute intervals). CCFLs give you the efficiency of a CFL without the delayed start-up (or the diminished lifetime from frequent power cycles).