We've covered various Christmas light topics over the years, and one topic that comes up often is the importance of choosing the right lights for your Christmas lighting display. With the right lights, your holiday decorations will look festive and bright. One topic we haven't covered as much is C7 and C9 bulbs. These are the classic Christmas light bulbs that have been around for ages. But what is the difference between them, and which should you choose? Today, we'll compare C7 and C9 Christmas lights, looking at size, brightness, wattage, and several other factors that will help you choose the best bulbs for your holiday lighting display.

Understanding C7 and C9 Christmas Lights

To better understand C9 and C7 Christmas lights, you must first understand how they got their names. Like any bulb, the names of these bulbs are a code that refers to the type of bulbs. In this case, the "C" indicates that the bulb has a 'candle' or 'cone' shape, and the number represents the bulb's diameter. C7 lights are 7/8th of an inch in diameter. C9 bulbs are much larger with a diameter of 1 1/8th inches.

Aside from this, what's the difference between C7 and C9 Christmas lights? There are several differences between these bulbs. Let's take a look at them.

Size and Appearance

The main difference between C7 and C9 light bulbs is the bulb size. Dimensions will vary depending on the manufacturer, but they typically measure:

C7 Bulbs: around 1.5 inches long and 1 inch in diameter
C9 Bulbs: around 2.25 inches long and 1.125 inches in diameter

Since C7 bulbs are smaller than C9 bulbs, they hit the 'middle ground' of bulb sizes. This smaller size allows them to be used for a wider range of holiday lighting applications. C9 bulbs, on the other hand, are far larger. They are best suited for areas that benefit from a larger, more visible bulb.

What about C6 lights? When shopping in store or online, you might notice C6 lights mixed in with C7 and C9s. C6 lights are typically found as LED bulbs, as incandescent versions have been phased out. Far smaller than C7s and C9s, they are more strawberry shaped and feature a faceted finish.

Brightness and Wattage

Brightness and wattage will vary slightly between incandescent C7 and C9 bulbs. As a rule, most manufacturers do not measure the brightness output (lumens) of Christmas lights since they are purely for decoration. To gauge the brightness of incandescent C9 and C7 bulbs, you need to take a look at the wattage.

C7 bulbs generally range from 5 to 7 watts. While bright, they aren't overpowering like larger bulbs. This makes C7 bulbs a popular choice for both indoor and outdoor displays. You will commonly use them to wrap columns and light Christmas trees.

C9 bulbs typically range from 7 to 10 watts. The higher wattage usage makes incandescent C9 bulbs generally brighter than C7 lights. The combination of their size and brightness makes C9s a more popular choice for outdoor applications, as these bulbs can be seen from a distance. They are most commonly used for lining roofs.

Voltage and Brightness: Many Christmas light manufacturers have begun making incandescent C7 and C9 bulbs that operate on 130 Volts as opposed to the traditional 120 Volts (the standard for all households). When used at the lower household voltage, the bulbs will last longer. The tradeoff, however, is they are slightly dimmer than 120V bulbs.

Base Size and Compatibility

Another big difference between C7 and C9 bulbs is their bases. While both utilize classic Edison screw bases, they are going to have different base sizes. C7 bulbs have a candelabra (E12) base that measures 12 millimeters in diameter. This is the same base used in many chandeliers and assorted decorative fixtures. C9 bulbs have a larger intermediate (E17) base, which has a diameter of 17 millimeters. The intermediate base is another common decorative fixture base.

Since the bases are different sizes, C7 and C9 lights can only be used with certain sockets. C7 bulbs will only fit C7 (or candelabra) sockets, while C9 bulbs will only work in C9 (or intermediate) sockets. If you try to mix them, they won't fit.

Energy Efficiency and LED Options

While incandescent C7 and C9 bulbs appear to have relatively low wattage compared to regular household bulbs, that wattage adds up quickly when putting together a full holiday display. In fact, using incandescents can severely limit the number of lights you have per circuit. This is where LED versions come in.

Featuring the classic look and bases of traditional incandescent bulbs, LED C7 and C9 bulbs use far less energy. At less than a watt each (depending on the manufacturer), these extremely energy-efficient Christmas lights allow you to use nearly three times as many lights per circuit while drastically cutting your holiday energy costs. The tables below break down the number of C7 bulbs and C9 bulbs depending on the bulb wattage and usable wattage of your circuit:

C7 Bulb Wattage	Bulbs per 15-Amp Circuit 1400 Usable Watts	Bulbs per 20-Amp Circuit 1920 Usable Watts
Incandescent @ 5W	288	384
LED @ 0.5W (VividCore)	3,600	4,800
LED @ 0.48W (VividCore Premium)	3,750	5,000

C9 Bulb Wattage	Bulbs per 15-Amp Circuit 1400 Usable Watts	Bulbs per 20-Amp Circuit 1920 Usable Watts
Incandescent @ 7W	205	274
LED @ 0.5W (VividCore)	3,600	4,800
LED @ 0.74W (VividCore Premium)	2,432	3,243

15-Amp circuits have a total of 1800 Watts, 20-Amp circuits have a total of 2400 Watts. For safety, you should only use 80% of the total wattage. Usable wattage is determined by multiplying the total wattage by 0.8.

Determining the Number of Bulbs: Want to learn how to determine how many incandescent and LED light bulbs you can safely use? Read our informative blog post: How to Calculate Maximum Runs from Wattage

Aside from energy conservation, LED bulbs last far longer than traditional incandescents. Many bulbs, such as VividCore and VividCore Premium, are rated to last up to 50,000 hours. This means these bulbs will last multiple seasons, cutting the money spent on replacements. These bulbs are also made using durable polycarbonate, so they won't break easily.

Another feature of C7 and C9 LED Christmas lights is that they are brighter than their incandescent counterparts. This is due to how the LEDs deliver light. If you've read any of our posts about how incandescent bulbs work, you know they lose over 80% of their light output as heat. LEDs don't have this issue. Since they generate very little heat, you get nearly all of the light output.

Ideal Applications for C7 and C9 Lights

C7 and C9 Christmas lights are versatile and can be used for a wide range of different applications. Since they are smaller in size, C7 lights are the best for both indoor and outdoor use. C9 lights are best suited for outdoor use. Their larger sizes make them perfect for when you want to make a bold statement or create a showy holiday lighting display. Here are some common applications:

C7 Bulbs	C9 Bulbs
Indoor Christmas Trees Mantels Banisters Outdoor Trees & Bushes Walkways & Driveways Porches Smaller Displays	Rooflines Fences & Posts Large Outdoor Trees Pathways Pillars Walkways & Driveways Larger Displays Commercial Displays

Color and Design Variations

Incandescent and LED C7 and C9 bulbs come in a wide variety of colors and envelope (the glass or plastic part of the bulb) variations. Incandescent versions are available in clear or colored versions. Clear bulbs will have a transparent glass envelope. Colored bulbs can either be transparent or opaque. Transparent color options will have coloring on the envelope, but you will be able to see through the bulb. Opaque bulbs will have a solid color that you cannot see through. Keep in mind, however, that incandescent bulbs will always emit a warm, yellow light regardless of the color of the glass.

LED C7 and C9 light bulbs are a little different. First, the envelope can have a smooth or faceted finish. Bulbs with a smooth finish mimic the appearance of classic Christmas lights, while bulbs with a faceted finish will have a twinkling effect. Second, LEDs are capable of emitting colored light. This allows them to produce various shades of white light (warm white, cool white, etc) and vivid colors. There are even color-changing options that slowly cycle through shades automatically.

Themes and Aesthetics

One of the best parts about creating an exceptional Christmas lighting display is choosing the theme. The theme will set the overall appearance of your display and dictate what type and color C9 or C7 lights you choose. LEDs tend to be used for more modern themes due to their brightness, whereas many opt for incandescents to capture the classic look of Christmas they grew up with. Here are some common themes:

Traditional - clear incandescent bulbs
LED Traditional - warm white or warm white deluxe LED bulbs
Traditional w/ Colored Lights - red, green, and warm white LED or incandescent bulbs
White Christmas - opaque white LED or incandescent bulbs
Winter Wonderland - white and blue LED bulbs
Northern Lights - purple, green, blue, and teal LED or incandescent bulbs
Candy Cane - red and white incandescent or LED bulbs

Additional Considerations for C7 vs. C9 Christmas Lights

As you choose which C9 and C7 bulbs work best for your Christmas lights, there are additional considerations you should take into account.

Safety Tips

Safety is paramount for any installation, regardless of installation location. Any lights used outside need to be outdoor-rated. This goes for extension cords, timers, power strips, and other accessories you pair with them. Your Christmas lights should also be installed using the appropriate clips to protect the installation surface and the lights.

You also need to ensure your lights don't become a safety hazard. Tips include keeping lights away from flammable materials, replacing failed bulbs as soon as possible, and not laying in areas prone to puddles. Learn more safety tips by reading our previous blog post, Your Guide to Choosing the Best Christmas Lights for Every Space.

Cost and Long-term Savings

Two considerations that go hand-in-hand are costs and long-term savings. When planning your Christmas lighting display, you need to consider the upfront cost of the lights, how much you will spend to power them, and how much you will spend on replacements during the season. Also consider bulb and light string longevity, accounting for potential future replacements.

Let's look at incandescent C7 and C9 bulbs. Upfront, these bulbs are very inexpensive. You can buy all the lights you need, plus extras, without spending a lot. However, due to their high wattage usage, you will have higher energy costs during the season. The high wattage also limits the number you can use on a single circuit. You may also go through multiple replacements due to bulbs reaching the end of their lifespan or breaking.

Now let's look at LED C7 and C9 bulbs. LEDs have a higher upfront cost than incandescent bulbs, but this becomes moot when you look at their efficiency and longevity. Since LED bulbs barely use any energy, their impact on your holiday season energy bill will be low. They pay for themselves, and you can use three times the amount per circuit. They are also extremely durable, able to withstand impacts and accidental drops, and will last several seasons. This means you won't be spending much on replacements.

Given this, which should you choose? Incandescents are great for small displays where you don't necessarily need a lot of lights, want to go with a classic-looking display, or when energy costs aren't a big issue. LED bulbs are the best choice when you want a lot of lights with lower energy costs.

So let's summarize: C7 bulbs are smaller bulbs with a candelabra base, use 5 to 7 watts, and are good for indoor and outdoor use. C9s are larger bulbs with an intermediate base, use 7 to 10 watts, and are best for outdoor use. LED options offer greater energy efficiency, longevity, and customization options when compared to traditional incandescent bulbs.

Remember to consider upfront costs, energy consumption, longevity, and safety when choosing between incandescent and LED bulbs to create a festive and cost-effective holiday lighting display. Need help finding the best C7 or C9 bulbs for your holiday display, home, or business? Call us today at 1-866-514-0132 to speak with one of our holiday lighting experts or visit our website to shop our Christmas lights.

Need help finding the best C7 or C9 bulbs for your holiday display, home, or business? Call us today at 1-866-514-0132 to speak with one of our holiday lighting experts or visit our website to shop our Christmas lights.