Holiday lights on a smart timer: sunset schedules, loads and tripped GFCIs

Timer, smart plug or smart outlet?

A smart plug is the right choice for most homes because sunset changes by more than an hour across the holiday season. Read the outdoor smart plug guide for ratings, covers and Wi-Fi tips.

Set a schedule that matches the day

1. On at sunset, with a short offset. “Sunset plus 10 minutes” keeps lights from coming on in bright daylight.
2. Off before bed. ESFI advises turning off indoor and outdoor electrical decorations before leaving home or going to sleep, so choose an off time of about 10 or 11 p.m.
3. Skip a morning on-time. Lights seldom need to be on at sunrise. If you want them, set a short window.
4. Use a group or scene. Put the front yard, roof and tree on their own plugs so you can turn them off separately.
5. Add a manual override. A wall button or a voice command is handy for guests.

Choose a plug that stores its schedule on the device. If a router reboot or outage knocks out the internet, a local schedule keeps working.

Count the load

CPSC says never to string together more than three sets of incandescent lights and never to overload outlets. LED strings change the math. ENERGY STAR says certified decorative light strings use about 92% less energy than conventional incandescent strings and can last up to ten times longer, and products labeled for outdoor use are subjected to weathering tests.

Use the wattage printed on each set. Example with label values: ten incandescent strings at 40 W each equal 400 W; ten LED strings at 3 W each equal 30 W. A 15 A, 120 V plug is limited to 1,800 W, but plan to stay well below it, and check the plug’s own label first because many smart plugs carry a lower rating.

What it costs: five hours a night for 40 nights at the EIA’s 18¢ per kWh. The incandescent strings use 400 W × 5 h × 40 ÷ 1,000 = 80 kWh, about $14.40. The LED strings use 30 W × 5 h × 40 ÷ 1,000 = 6 kWh, about $1.08. The DOE formula is the same for any device; use the device energy cost calculator for your own display.

Outdoor-rated gear only

• Lights and cords. ESFI says all extension cords and electrical decorations used outdoors should be marked for outdoor use. Look for a listing from a recognized testing laboratory, a point CPSC also makes.
• Match amps. Match the amperage of the lights to the rating of the extension cord, keep cords out of snow and standing water, and do not chain cords together.
• Inspect first. Check lights, decorations and cords for damage before use. Throw out sets with cracked sockets, frayed wire or loose connections.
• Fasten securely. Use insulated staples or hooks made for lights. Avoid nails or tacks that can pierce wires.
• Power lines. ESFI says to keep yourself and your equipment at least 10 feet from power lines.

Why the GFCI trips in the rain

A GFCI shuts off when it senses current leaking along a path other than the intended one, such as through water. Rain or snow on plug connections, a cord lying in a puddle, a damaged strand or too many sets can all cause it. Work through it in this order:

1. Unplug every cord and the smart plug from the outlet.
2. Dry the plug ends and connections. Raise them off the ground and make a drip loop so water runs off before it reaches the plug.
3. Press RESET, then add one set at a time until it trips again. The last set added is the likely culprit; leave it out.
4. Use connection covers or a larger while-in-use cover over plug-to-cord junctions.
5. If the GFCI trips repeatedly on dry, calm days, the outlet may have failed or there may be a wiring fault. Do not bypass the GFCI. Hire a licensed electrician.

Smarter tricks that stay safe

• Pair the timer with a motion-triggered porch light so the entrance is lit after the display turns off (outdoor smart lighting).
• Keep one plug per display zone so a tripped GFCI affects only one area.
• For a renter with no outdoor outlet, use battery-powered LED strings with a built-in timer rather than a cord through a window.
• Store lights loosely wrapped and dry, and test them before the next season.