What size/type wire for a 300ft run from house to shed?
Just drop a conduit in there instead, you'll thank yourself later
Instead of rushing to buy wire and getting the wrong thing, then having to dig it up later, why don't you get yourself some fat PVC conduit (such as 1.5&quot; or 2&quot;) and lay that in the trench instead, with prefabricated sweeps and expansion fittings at each end? That way, you can pull the wire at your leisure, and don't have to worry about digging things back up if you want to upgrade later.  While you're at it, you can also lay a second conduit, say 1&quot;, if you want to to provide a convenient way to run a telecom cable (of any sort: phone, Ethernet, fiber, you name it) out to the shed.