Christmas lights come in three common sizes, and the one that looks best on your tree can look lost on your roof. Lighting suppliers such as 1000Bulbs say the C9 is the bulb most commonly used for lining roofs. The C7 and the mini light each have their own jobs.
The three sizes
| Mini | C7 | C9 | |
|---|---|---|---|
| Bulb size | Smaller than a fingertip | About 1 inch wide, 1½ inches tall | About 1⅛ inches wide, 2¼ inches tall |
| Socket | Built into the string | E12 (candelabra) base | E17 (intermediate) base |
| Old incandescent bulb | About 0.4 watt | About 5 to 7 watts | About 7 to 10 watts |
| Best for | Trees, shrubs, railings | Bushes, small trees, smaller displays | Rooflines, peaks, anything you see from the street |
The two big bulbs use different bases, so a C9 won't screw into a C7 socket, and a C7 won't fit a C9 socket.
Why the C9 suits a roofline
You see a roofline from a distance. It sits one or two stories up, and most people look at it from the sidewalk or a passing car. A bigger bulb holds a clean line at that distance. A C7 looks small from the street, and mini lights blur together.
LED or incandescent
We hang LED C9s. An LED C9 draws less than a watt, about half a watt for a typical commercial bulb, while an old incandescent C9 draws 7 watts or more, according to 1000Bulbs.
On a 100-foot roofline with a bulb every foot, running six hours a night:
- LED: about 50 watts, roughly $1 to $2 a month at Iowa's average residential rate of about 16 cents per kWh
- Incandescent: about 700 watts, roughly $20 a month at the same Iowa rate
Store strings vs. commercial strands
A string from the hardware store comes in a fixed length, with the bulbs at fixed spacing. Your roof comes in its own lengths. You end up a few feet short on one run and holding a loop of extra on the next.
Commercial C9s start as a spool of wire with the sockets built in. The installer cuts each strand to the measured length of one section of your roof and puts a bulb in every socket, so the line starts and stops where the roof does. A bulb about every 12 inches is common spacing on a roofline. Closer spacing reads brighter from the street, and wider spacing starts to look gappy once you are a few houses away.
Mixing sizes on one house
Plenty of houses use more than one size, and that is fine as long as each size has its own job. C9s go where the street looks: the gutter line, the peaks and the garage. A wrapped tree in the yard usually gets mini lights, because a C9 on a branch looks heavy up close. Bushes by the front door can take C7s or minis.
What looks wrong is changing size partway along one line. A C9 run that turns into C7s halfway across a gutter reads as a mistake from the sidewalk, so keep every roofline run to one bulb.
What we use
Shimmer & Shine installs commercial-grade LED C9s on every seasonal job. You can pick warm white, multicolor, red and white, or a custom mix, all at the same price. Color changing C9s, which you control from your phone, are priced on their own, and so are trees and wreaths.
Which one to pick
- Roofline, peaks and gutters: C9
- Bushes and railings: C7 or minis
- Tree trunks and branches: minis
See C9s on your house
Send your address on the estimate form. Tate measures your roofline from satellite imagery and texts you a ballpark, usually the same day.
Common questions
Which is bigger, C7 or C9?
The C9. It measures about 1⅛ inches wide and 2¼ inches tall, against about 1 inch by 1½ inches for a C7.
Can I put C9 bulbs in C7 sockets?
No. A C7 uses an E12 candelabra base and a C9 uses a larger E17 base, so neither fits the other's socket.
Will LED C9 lights raise my electric bill?
Barely. An LED C9 draws about half a watt, so a 100-foot roofline with a bulb every foot uses around 50 watts. Six hours a night at Iowa's average residential rate comes to roughly a dollar or two a month.
Do C9 lights come in colors?
Yes. Warm white, multicolor, red and white and custom mixes all use the same C9 bulb, and we charge the same for each. Color changing C9s, which you control from your phone, are priced on their own.
