This is one of those threads where you are getting advice that's all over the place. Some good, some not so good.
There really is no way to know what else is on the line until you test it. It could be pretty much free to do with as you wish, or it could be supplying power to a dozen things that are close to maxing it out.
A simple rule of thumb is tha a 100 watt light bulb uses one amp of power. There are other factors in this, but it's a good rule for simple math. Use a 40 watt bulb and it's less then half an amp per bulb.
Step one would be to find out what's on that line, and how much power is being used.
Do the math and figure out what is left. You never want to max out a line because that's when you start tripping breakers.
Once you know what you have available to use, then you need to create a plan of how many lights you can install, and how many watts you can put on each light. Lower wattage means more lights.
Solar lights will dissapoint you. They are probably the only things out there that everyone who has them, complains about them. Plug in, low wattage lights work well, but you get what you pay for. Plastic ones are cheaper, they work fine for awhile, but they start to fall apart after a few years. Metal is much better if you want to spend the money. You can really increase you number of lights by installing some outlets to plug in a few lines of low voltage lights.
Before pulling the light pole, look real close at the base of the light, and around it in the bushes. Ideally, it should have been installed with a junction box either inside of it, or next to it. If so, then you just run your lines off of the junction box.
Another thing to consider before pulling the light out is to figure out where the wire runs in the ground and see if you can dig it up. I don't know if you want that light where it is, or even want it at all, but if you like it, then leaving it alone and redoing the wiring is the easier choice.
I like grey plastic for my junction boxes and conduit. I've replaced and seen allot of metal junction boxes that have rotted away. They sort of melt, or whatever happens to them. I've seen it so many times that it's almost common. It could be fertilizers or pestisides that cause this, but whatever the reason, I don't buy metal for junction boxes anymore.
Install the junction boxes up in the air, above the grade of the ground. It will be kind of ugly, so think of planting somthing in front of them in your plan.
You should have a junction box at every light. If it's an outlet, that is also a junction box, and you could add an outlet to every junction box for just a light to give yourself more options. It's more work and money for the covers, but worthwhile if you can see a need for them. It's not hard to add an outlet to a junction box later off if you need it either.
You can run your lights like the spokes of a wheel with one main junction box in the middle and each run going out from there, or you can daisy chain them and go from light to light to light. Or a combination of both. It's pretty simple as long as you are on the same circuit and keep your wires matched up. Black to black and white to white.
Again, make a plan. Put it down on paper and spend some time rethinking it. Draw a map how you want the lines to run and think about what you will be digging through. Trees really suck when digging trenches because of those roots. I use a sawzall to cut roots with a prunning blade. When bidding a job that requires digging and trees, I add that to my bid, including a three pack of new blades.
Good luck,
Eddie
but it's a good thing that's how you want it to work, cause that's the only way it can work (on that existing switched circuit).
