I am having the electric company transition my wiring from overhead to underground, upgrade my service (it might only be 60amp right now) to 200amp, having another company replace my panel with a new one (200amp), and installing a pedestal to make it solar ready if I ever choose to go that route.
The pricing on that portion of it seemed pretty fair but they also estimated the power to the detached garage and it's way too high in my opinion. Much higher than I would have imagined. They were estimating $25 per foot for (hand?)trenching and running wire (total of $3375) and then a few hundred more for some basic light switch installs, etc. This seemed rather expensive to me.
The house is roughly 135 feet away from the garage. I will only add a couple outlets (or an outlet strip), light switch, and some lighting. I expect this to basically be a 20amp circuit.
According to this voltage calculator, it would recommend this for copper:
1 conductors per phase utilizing a #6 Copper conductor will limit the voltage drop to 1.99% or less when supplying 20.0 amps for 135 feet on a 120 volt system.
and this for aluminum
1 conductors per phase utilizing a #4 Aluminum conductor will limit the voltage drop to 2.06% or less when supplying 20.0 amps for 135 feet on a 120 volt system.
I'm assuming those are both THHN, whatever that means. I'm not sure I am looking at the proper wires from HomeDepot but I assume the difference will be negligible and it would cost me a few hundred dollars for the wire itself. Then to rent a trencher it would only cost about $100. Then to do the wiring it would mostly just cost me time.
Is this something I could do myself? Am I missing some aspect of this that would make it harder than it really is? What wiring should I be looking at? Does it make sense to use conduit here or can I get away with in-ground wiring?