So, what is the difference between SPT-1 and SPT-2?
When shopping for Christmas light strings specifications you might have noticed are the SPT-1 and SPT-2 specifications. You'll especially see these terms when shopping for C7 and C9 Christmas bulbs and cords.
This spec is simply an indicator of the thickness and durability of the insulation.
Most of the time, Christmas light cords don't list this as a spec and in those cases, you can almost always assume that the cord is SPT-1 which is a standard commercial grade cord.
A thicker, more durable insulation is SPT-2 rated insulation. We started carrying the cord with this thicker insulation a few years ago to meet the needs of commercial customers. We now carry a wide variety of wire colors and socket spacings with SPT-2 rating.
What current is SPT-1 or SPT-2 rated for?
There is some misinformation on the internet that a higher SPT rating indicates that the wire can take a higher current - this argument is used to say that SPT-1 can't carry the same 10 amps as the SPT-2 version. This is not accurate information. The amount of current a cable or wire is rated for is strictly a function of the copper used for that cord.
Please remember with all things electrical that if you have a serious question about what wire to choose and how it will work in your situation that a Master Electrician is the first person to consult. I suggest that you consult with one on any project where cutting of 1000 foot spools to custom lengths is involved - especially at commercial/retail installations.