When someone says they are looking for vintage or traditional style Christmas lights they are generally referring to the C7 or C9 screw in style Christmas light bulbs. These bulbs are classic and easy to replace when bulbs burn out or you are looking for extra lights that can match.
C7 and C9 Christmas lights have been around for decades, they look just as wonderful and classy today as they did in the 50's and they continue to be a standard in holiday decorating. One of the best features about using these types of lights is they can be purchased year to year without the style changing drastically.
When you purchase light sets or specialty type light sets at some of the big box stores you are almost guaranteed to never find an identical product ever again and then if you ever have a problem with the lights you will have to throw out the whole style and start over from scratch.
Most online Christmas light retailers will always carry C7 and C9 Christmas lights and you can be assured that it won't be overly difficult to match styles and colors in the future.
So which size should you choose, C7 or C9?
The C7 Christmas light is the size of a standard night light bulb. It has a candelabra base (E12/C7 Base) that can generally fit into chandeliers. This C7 sized Christmas light bulb is a great choice for residential homes that are just one story tall. The C7 Christmas light also is great for putting on large outdoor Christmas trees, lining walkways or installing on pole decorations and signs. Because of their smaller size C7 light bulbs also tend to break less than their bigger counterpart, the C9 Christmas light. A standard C7 Christmas light generally uses 5 watts of power per bulb for incandescent styles and .5 watts for LED commercial grade bulbs.
C9 Christmas lights are the number one choice for commercial decorators or on residential jobs that are taller than one story. The bigger bulb and brighter wattage make these more noticeable from higher up and will really help make your roof line pop at night when they come on. They are similar to working with a C7 but the base is bigger (they can only fit in a C9 base, they are not interchangeable with a C7 base), and you will have to have more power available to run C9 Christmas lights. The average C9 incandescent bulb uses 7 watts of power and the average C9 LED (if it is commercial grade and not a mini light with a cap over it like most big box stores sell).