Holiday Lights: How Many You Need, Which to Buy and How to Hang Them Safely

How do I work out how many strands I need?

Measure each continuous section you’ll light, such as the front eave, the garage or a window, as its own run. Divide each run by the strand’s lighted length and round up, then add the runs together only after rounding.

Adding first undercounts. A 35 ft roofline and two 3 × 4 ft windows come to 63 ft, which divided by 25-ft strands would round to 3. As three separate runs they need 4: two for the roofline and one for each window, each with lit length to spare.

What’s the difference between lighted length and cord length?

Lighted length is the section with bulbs. The cord or package length also includes the lead and tail cords, so it’s longer. Plan with the lighted length; using the package length makes every strand look like it covers more than it does.

How many lights do I need for a tree or shrubs?

It depends on the size and how closely you wrap. Spacing matters most: for a 6 ft tree 4 ft wide at the base, passes 12 inches apart take about 40 ft of lights, and passes 6 inches apart about 79 ft. Shrubs work the same way with rows across the surface. Treat these as estimates and buy with that in mind; outlines like rooflines and windows can be measured exactly.

How many clips do I need?

Divide each outlined run by your clip spacing, round up, and add one per run; wrapped railings, trees and shrubs take none. Use clips, not nails, so the cords aren’t damaged⁴, and nails or staples can cut through the wire insulation⁷. Clips are made for particular surfaces (gutters, shingles, railings, brick), so buy ones that fit where the lights will hang.

Are my lights rated for outdoor use?

Check before you hang them. Some lights are only for indoor or outdoor use, not both⁴. Check outdoor lights for labels showing they’re certified for outdoor use, and only use lights tested for safety by a nationally recognized testing laboratory².

On UL-certified strings, the holographic label tells you: green means indoor use only, red means indoor or outdoor use³. ENERGY STAR light strings labelled for outdoor use have also been weathering tested⁶.

Should I buy LED or incandescent lights?

LED, for most displays. ENERGY STAR certified decorative light strings use about 92% less energy than incandescent strings, can last up to 10 times longer, and are cool to the touch⁶. LED packages also usually say how many strings can be connected end to end⁷.

To estimate running cost, multiply strands × watts per strand × hours a day × days, divide by 1,000 for kilowatt-hours, and multiply by your electricity rate. For example, 11 strands at 4.8 W each, 6 hours a night for 40 nights, use 12.7 kWh; at $0.31 per kWh that’s $3.93.

Example wattage and rate to show the arithmetic. Use the watts on your own label and your utility’s rate.

Warm white, cool white or multicolor?

That’s a matter of taste, and it doesn’t change how many strands you need. If you’re adding to lights you already own, match the color and bulb style so the runs look the same.

How many strands can I connect end to end?

Only as many as the manufacturer’s instructions allow⁴. The Consumer Product Safety Commission says never to string together more than three sets of incandescent lights and never to overload outlets¹. A long roofline may need power at more than one point, or a product that allows more strands. The calculator flags runs that need more strands than the limit you enter.

What about extension cords and outlets?

Use extension cords marked for outdoor use, match the amperage your lights need to the cord’s rating⁵, and check each cord is rated for the intended use and in good condition². Plug outdoor lights only into a GFCI-protected outlet or a portable GFCI²⁵.

Don’t overload outlets, and don’t run cords through doors or windows, where they can be pinched and damaged⁵. Keep cords and light strings clear of snow and standing water⁵. CalcBrite doesn’t size cords or approve electrical loads.

Should I leave the lights on overnight?

No. Turn off all light strings and decorations before leaving home or going to bed⁴⁵. An outdoor-rated timer does that for you every night.

What should I check before hanging lights?

• Check each set, new or old, for broken or cracked sockets, frayed or bare wires, or loose connections, and throw out damaged sets².
• Replace burned-out bulbs promptly: empty sockets can make the whole string overheat⁷. Unplug decorations before replacing bulbs or fuses⁵.
• Hang lights with clips, not nails or staples⁴⁷, and fasten them securely without damaging the cord’s insulation⁵.
• Don’t use electric lights on a metallic tree².

How do I use a ladder safely for roofline lights?

Inspect the ladder for loose or missing screws, hinges, bolts and nuts, and use a wooden or fiberglass ladder outdoors, since metal ladders conduct electricity. The ladder should extend at least three feet past the edge of the roof, and you and your equipment should stay at least 10 feet from power lines⁵.

Should I hire an installer?

High rooflines and tall trees are elevated work, so a professional installer is worth considering. Installers price by the job: share your areas, approximate footage, number of separate runs and whether you’ll supply the lights, and ask whether lights, clips, installation, removal and storage are included. The calculator writes that request for you; it doesn’t estimate labor prices.

When should outdoor lights come down?

Within about 90 days. The longer exterior lights stay up, the more likely they are to be damaged by weather and animals chewing on them⁷.

How should I store holiday lights?

Inspect each set as you take it down and throw out any that are damaged². Tangled lights lead to damaged cords and broken sockets, so coil each string loosely around a stiff piece of cardboard, wrap it in paper or fabric to protect the bulbs, and store it in a sturdy container until next year⁷. Labelling each one with its lighted length makes next year’s plan quicker.