Ideas & guides · Lighting

What Extension Cord Do Outdoor Decorations Need?

The lights at the far end of the run are noticeably dimmer than the ones near the house, and the cord is warm in the middle. Is that normal?

6 minute read.

The two things on the jacket that matter

Everything you need is printed on the cord itself, in small raised letters along the jacket. Two parts of it decide whether the cord is right.

The first is a W, usually as part of a code like SJTW or SJEOW. The W means the jacket is rated for wet and cold conditions. A cord without one is an indoor cord, and an indoor cord outdoors in December goes stiff, then cracks at the bends, and the cracks are where water gets to copper.

The second is the gauge, written as a number and the letters AWG. This is where people go wrong, because the scale runs backwards: 12 gauge is thicker than 14, which is thicker than 16. Lower number, heavier cord, more current it can carry over a longer distance without losing voltage.

A third marking is worth a glance: the amp or watt rating, usually on the tag. If a cord does not state one at all, that is itself informative.

What gauge for what distance

Sized for the loads a yard display actually puts on a cord, which is a few amps run continuously for six or seven hours rather than a brief heavy draw.

A cord warm enough to notice is a cord converting your electricity into heat instead of delivering it. It is both the waste and the warning.

Why the far end goes dim

Every foot of cable has a small resistance, and pushing current through resistance costs voltage. The longer and thinner the cable, the more of the 120 volts is spent getting there rather than arriving.

LEDs mostly shrug this off, which is why an all-LED display can survive a bad cord and only look slightly wrong. Incandescent mini lights show it immediately and go orange. Inflatable blowers are the ones that genuinely suffer: a motor fed low voltage draws more current to do the same work, gets hot, and either underinflates the piece or shortens its own life.

The practical rule is to keep any one run as short as the yard allows, and to run two shorter cords from two outlets rather than one long one daisy-chained across the lawn. Two 50 ft runs are electrically much better than one 100 ft run, even though they cost about the same.

Connections, which is where the failures actually happen

Cords rarely fail along their length. They fail where two of them meet, because that is where water gets in, and a joint lying on wet grass is a joint sitting in a puddle by Tuesday.

Give every connection a drip loop: let the cord dip below the joint before it rises into it, so water running down the cable falls off the bottom of the loop instead of tracking into the plug. It costs nothing and two seconds, and it is the single highest-value habit in this entire article.

Keep joints off the ground where you can — clipped to a fence rail, a stake, anything a few inches up. Where they must be near the ground, a connection cover, which is a plastic clamshell costing a few dollars, does the job properly. Taping a joint with electrical tape does not: tape traps the water that does get in and holds it against the metal.

And do not run a cord under a rug, a doormat or a path of stepping stones. Every year somebody does it to hide the cable and produces a cord that is being slowly crushed with nobody able to see the damage.

Where this usually goes wrong

Buying by length and price, and ignoring the gauge

A 100 ft 16 gauge cord and a 100 ft 12 gauge cord sit next to each other on the shelf and one is half the price. They are not the same product. At that distance the cheap one will dim the far end of the display and warm up doing it.

Daisy-chaining three cords to reach the corner

Each joint is a place for water to get in and each length adds voltage drop. One correctly sized cord beats three short ones end to end, and two runs from two outlets beat both.

Using an indoor cord because it is only for a few weeks

A few weeks is the whole season, in the wet and the cold, which is exactly the condition an indoor jacket is not rated for. It goes stiff and cracks at the bends, and the cracks are not visible until you go looking.

Leaving the reel coiled

A cord run at anything near its rating while still wound on its reel cannot shed heat, because every turn is warming the turn beside it. Unwind the whole thing even when you only need half of it.