Light Bulbs, Tubes and LED Strips

Base, shape and tube code decide whether a lamp fits

A lamp has to match its socket before anything else. Screw bases such as E26 and E27 (medium) are common, smaller ones like E12 and E5 suit candelabra and indicator lamps, and pin or prong bases belong to fluorescent and compact tubes. Fluorescent tubes carry a code such as T5, T8 or T12, where the number is the diameter in eighths of an inch, followed by the wattage and length. Metal halide and high-pressure sodium lamps are made for a specific ballast and cannot be swapped for each other.

Color temperature, lumens and strip voltage

Color temperature in kelvin sets the mood: around 2700 to 3000 K is warm white, 3500 to 4100 K is neutral, and 5000 to 6500 K is cool daylight white. Compare brightness in lumens, not watts, since an LED gives the light of an incandescent bulb for a fraction of the power. LED strips are rated by voltage, such as 12 V or 24 V, and need a matching driver. An LED tube in a fluorescent fixture may need the ballast removed or bypassed, so follow the tube maker's instructions.

Questions about Light Bulbs, Tubes and LED Strips

What do T5, T8 and T12 mean?

The T stands for tubular and the number is the tube diameter in eighths of an inch: a T5 is 5/8 inch, a T8 is 1 inch and a T12 is 1.5 inches. The tube must also match the fixture's pin base and ballast.

Can I use an LED tube in a fluorescent fixture?

Often, but check the type. Some LED tubes work with the existing ballast, while others need it removed or bypassed so mains power goes straight to the sockets. The tube's instructions say which, and mixing methods can be unsafe.

What does warm white or cool white mean?

It describes the color of the light. Warm white, near 2700 K, looks yellowish like an incandescent bulb, while cool white, around 4000 K or higher, looks bluer and crisper. Warm tones suit living areas, cooler tones suit work areas and garages.