When planning an outdoor Christmas decorating project or if you have any other outdoor electrical needs, the question about what type of cord to use may arise. Some people research the differences between SPT-1 and SPT-2 cords online with the belief that the information that they will find is correct. However, there are several common misconceptions about these cords online, and you do not want to be swayed into making a less than ideal decision based on erroneous information. Before you install any type of outdoor lights, focus your attention on these factors in order to make the right decision for your needs and goals.

The Primary Difference Between SPT-1 and SPT-2 Cords
When trying to decide which type of cord is most ideal for your upcoming project, you need to understand how these two types of cords differ from each other. SPT-1 cords have an insulation thickness of .03 inches, and SPT-2 cords have an insulation thickness of .045 inches. Some online sources indicate that the greater thickness of the insulation in the SPT-2 cords means that the cords can carry more amperage. This is incorrect, so you should avoid making an amperage decision based on the thickness of the insulation. The actual size of the wire is based on the gauge. Both SPT-1 and SPT-2 cords are available in 16 and 18-gauge thicknesses. However most of the time 18 gauge wire is what is sold for Christmas lights.  So you must keep this in mind because 18 gauge wire is rated to handle only 10 Amps of power for runs between 0 and 50 feet.  The attenuation of the line continues to increase and this means the longer the cord the less amperage it can handle so for runs over 150 feet the line can only handle about 5 Amps.

The Impact of Weather Conditions on Cords
Amperage is not the only factor to consider when you are selecting a cord for your Christmas decorations or other outdoor electrical needs. The thickness of the wire is critical when you plan to leave the cord exposed to UV light for a lengthy period of time. UV rays can easily deteriorate the insulation on the cord, so a thicker insulation on the cords is ideal for long-term use outdoors. It may also be important if you live in a sunny climate and plan to leave the cords exposed to the elements for even a relatively short period of time.

The other weather-related factor to consider is the outdoor temperature and exposure to wind. In a very chilly, windy climate, the outer covering on the cord can crack or break. Therefore, insulation becomes more important for both sunny conditions as well as colder conditions. This is most important to consider if your cords will be exposed to the elements for a longer period of time. 

Our Decision
Usually as professional Christmas light installers we choose SPT-2 lines for the fact that the cost difference is minimal but it provides better protection.  The thicker line also provides a little better protection against squirrels and rabbits.  Those little boogers love to chew line in trees and on the ground.  Almost all of our projects are less than 90 days for installation so we don't have a huge issue with degradation but the cost savings isn't really worth the thicker insulation.  Those are the reasons that we purchase SPT-2 line for most projects.

Your Decision
When you take a closer look at SPT-1 and SPT-2 cords for your outdoor project, you will find that SPT-1 cords are usually more affordable than SPT-2 cords. You understandably want to save money on your cord purchase, but you also need to think about the condition of your cords when they are exposed to the elements. Damaged cords can result in an increased fire risk and other hazards. Therefore, regardless of the type of cord that you select, inspect it periodically for signs of wear or damage.