C9 LED vs Incandescent Bulbs: Which Is Right for Your Roofline?

C9 is the classic Christmas bulb, the fat teardrop shape on a screw base that lined rooflines across Canada long before anyone had heard of an LED. The shape has not changed. What is inside it has. Faceted LED C9s from Holiday Lights Direct use the same E17 base and the same socket lines as the old incandescent bulbs, which means the two are directly interchangeable and the choice comes down to how they look, what they cost to run and how they hold up on a roof in February. Here is how they compare, criterion by criterion.

The short version

• Brightness: comparable from the street, with LEDs giving cleaner, more saturated colour and incandescents a softer, warmer glow.
• Power: incandescent C9s are commonly around 7 watts each; LEDs use a small fraction of that, so you can run far more bulbs on one circuit.
• Lifespan: LEDs are rated for tens of thousands of hours; filaments burn out in a few hundred to a few thousand.
• Cold weather: LEDs start instantly at any Canadian winter temperature; filament bulbs are stressed by every cold start.
• Retrofit: LED C9s screw straight into existing E17 socket lines. No rewiring needed if the line is sound.

Brightness and how it reads from the street

The worry most people have about switching is that LEDs will look dim or cold. That was fair for early LED strings; it is not true of a modern faceted C9. The bulb body is designed to spread the light from the diode across the whole lens, so from the sidewalk the bulb reads as a solid glowing shape rather than a bright point with a dark shell around it. Side by side on the same eave, a warm white LED C9 and an incandescent C9 look close in brightness, and the LED usually looks slightly crisper because its colour is purer.

Where the two differ is the character of the light. An incandescent filament produces a broad, orange-tinted glow that many people associate with childhood displays. LEDs produce a narrower, more saturated colour. Warm white LED C9s are tuned to sit close to that traditional look; cool white is a bluer, brighter white that suits modern homes and commercial buildings. If you want the nostalgic look, choose warm white LED rather than assuming you need incandescent.

Power draw and how many bulbs fit on a circuit

This is the biggest practical difference and the one that changes how you design the display. An incandescent C9 is commonly rated around 7 watts. A hundred of them draw roughly 700 watts, which on a 120 volt circuit is close to 6 amps. That is most of what a typical household outdoor circuit can spare once the porch light, the inflatable and the garage freezer are counted, which is why incandescent runs had to be short. Faceted LED C9s draw a small fraction of that per bulb. Check the wattage on the product page and do the math for your own bulb count, but the practical result is that a whole roofline of LED C9s often draws less than a single short incandescent string.

• Work out current by adding the watts of every bulb on the run and dividing by 120.
• Compare that figure with the rating printed on the socket wire and the plug, and stay well under the lowest of them.
• SPT-2 18 AWG wire is commonly rated at 10 amps in the trade; with incandescent C9s that limit arrives quickly, with LEDs it rarely comes into play.
• Then look at the breaker: everything plugged into the same outdoor circuit shares it.

Colour options

Holiday Lights Direct stocks faceted C9 LEDs in warm white, cool white, red, green, blue, orange, yellow, pink, purple and multicolour, in packs of 25 for a single home and 500 for installers. Incandescent C9 colour comes from a coating on the glass over a white-hot filament, which is why old red and blue bulbs fade to pink and pale grey after a few seasons in the sun and why a mixed string never quite matches. LED colour is produced by the diode itself, so a red bulb is red from the first night to the last, and a run of blue bought this year matches a run bought next year. Pink, purple and orange in particular are colours that incandescent never did well and LED does easily.

The faceted lens look

The faceted lens is the detail that makes a modern LED C9 look like a proper Christmas bulb rather than a plastic cap. The lens surface is moulded into many small flat faces, and each face catches and scatters the light from the diode inside. Two things happen. From a distance the whole bulb glows evenly, with no hot spot at the base. Up close, and especially when there is snow on the roof to bounce the light back, the facets sparkle as you move, which is the effect people are describing when they say a display twinkles. Incandescent C9s have a smooth glass shell and glow evenly because the filament heats the whole coating, so they do not sparkle in the same way.

Lifespan and durability

A filament is a thin wire heated until it glows, and every hour it runs it gets a little thinner. Incandescent C9s are typically rated for a few hundred to a few thousand hours, and in practice a roofline string from the hardware store loses a handful of bulbs every season. LEDs have no filament to break and are rated for tens of thousands of hours. Run six hours a night for the two months most displays are up, that is a difference between replacing bulbs every year and not thinking about it for many years.

Durability on the roof favours LED too. The bulb body is plastic rather than glass, so a dropped bulb bounces instead of shattering and a bulb knocked by a ladder rail on the way down in January survives. Incandescent glass also runs hot, and a hot bulb resting against a vinyl soffit or a plastic clip is not ideal.

Cold-start behaviour

Canadian displays switch on at dusk when it may be minus twenty, and the moment of switch-on is the hardest part of an incandescent bulb's life. A cold filament has low resistance, so it takes a surge of current for a fraction of a second before it heats up, and that surge is what usually breaks an ageing filament. Bulbs seem to fail at switch-on rather than mid-evening because that is exactly when they do fail. LEDs have no filament and no surge. They reach full brightness instantly in any temperature you will see in Ontario or anywhere else in Canada, and cold does not shorten their life.

Retrofitting an incandescent socket line with LED C9s

If you already own an incandescent C9 line, you do not need to throw it out. The sockets are E17, the same base the faceted LED C9s use, so a retrofit is mostly unscrewing old bulbs and screwing in new ones. Before you do, inspect the line, because an old socket wire has usually spent years in the sun and on the roof.

• Unplug the line and look at every socket. Cracked, discoloured or corroded sockets should be cut out and replaced with a replacement E17 socket rather than reused.
• Check the cord for cracked or brittle insulation, especially near the plugs and at any spot that sat over a shingle edge. If the jacket crumbles when you flex it, replace the line with new empty socket wire.
• Check the plug. If the original moulded plug is damaged or the cord is cut, fit a new SPT-2 vampire plug that matches the cord type printed on the jacket.
• Screw in the LED bulbs snugly, fill every socket and test flat on the ground before hanging.
• Do not mix LED and incandescent bulbs on the same run. The load math is simpler and the colour matches better if each run is one bulb type.
• Once the line is all LED, the old rule about only chaining a couple of strings per outlet no longer applies in the same way, but re-do the wattage math before you extend it.

Cost of ownership in general terms

Incandescent C9s are cheaper to buy per bulb, and if purchase price were the only cost the comparison would end there. It is not. The electricity difference is large: a display that once drew close to a full circuit now draws a fraction of it, and that shows up on the bill over a season of evenings. Replacement is ongoing: a few dead bulbs on every run, every year, plus the ladder trips to find them. And the design cost is real: incandescent limits how many bulbs one outlet can feed, which often means an extra cord across the driveway or a smaller display than you wanted. LED removes all three. Over several seasons the faceted LED C9 costs less to own and looks the same or better every one of those seasons. Current pricing is on the product page.

When incandescent still makes sense

There are a few. If you have a box of working incandescent bulbs and a short line that sits on a dedicated outlet, using them until they fail costs nothing. Some people genuinely prefer the softer glow and are willing to pay for it. And some heritage displays are kept incandescent for the sake of matching what has always been there. For a new install, a retrofit, or anything you are being paid to hang for a customer, LED is the practical choice.

The verdict

For a roofline in Canada, faceted LED C9s win on power, lifespan, colour consistency, cold-weather reliability and cost of ownership, and they match incandescent on brightness while adding the sparkle of the faceted lens. The E17 base means the switch is a bulb swap, not a rebuild. Holiday Lights Direct ships C9 LED bulbs in every colour, with the empty socket wire, SPT-2 plugs and replacement sockets to build or repair the lines they go on, from London, Ontario to anywhere in Canada. Homeowners can start with a 25 pack; installers and municipalities should ask about the pro programs.