C9 and C7 Christmas bulbs are very popular choices for roof lines, but planning between LED and incandescent can be extremely different. If you need 300 ft. of C9 lights to cover all the roof lines of your home with traditional 12 inch spacing between each bulb, you're looking at 300 bulbs. Incandescent bulbs will look incredible, but will take 2,100 watts to power. LED bulbs will also look impressive, but will only require 29 watts. The wattage difference is extreme!
Both LED and incandescent lights in this example have 25 bulbs per string, which is very common. With incandescent, only 2 strings can be connected end-to-end, which means you'll need 6 different plug outlets. With the LED option, up to 87 strings can be connected together, which means the 12 you need for this project can be connected end-to-end and then plugged into a single outlet.
Tip: Because the incandescent option requires 2,100 watts, which is more than most household circuits can handle, you will need to separate your light runs onto different household circuits. This is not difficult, but it requires you to know which plugs in your house to use...otherwise you'll be running to the circuit breaker box often to flip blown fuses. The other planning consideration with this scenario is that you can only run 2 incandescent strings end-to-end. This means you have a maximum of 50 ft. to work with before you have to switch to a different plug outlet with a new run of your lights. Often times this method involves the use of extension cords or carefully planning various rooms in your house that have access to roof lines. There are easier planning options that include going with commercial grade, heavier gauge wiring so you can include more bulbs in larger runs, but this is also more expensive.
Why even consider incandescent? Granted, they're more difficult to properly plan for, but incandescent Christmas lights tend to be less expensive than LEDs, so if initial cost is a critical planning aspect for your project, incandescent may be a good option. While LED lights save money long-term, they often cost more up front. If you only use your Christmas lights sparingly a few weeks out of the year, you may not see the energy savings for several seasons which makes incandescent bulbs a popular choice. Also, many people like the look of incandescent bulbs because of the unique light halo they produce. They have that nostalgic quality that LED bulbs do not. Both bulb options can look fantastic, but incandescent options like this simply require more planning to do properly.