How far can you run a 14 gauge electrical wire?

You can run it as far as you want, knowing that the farther you go, the more voltage drop will occur under load. If you have a very small load, you can run 14 AWG for hundreds of feet.

For instance, 14 AWG copper THHN 90C in conduit with 3 percent voltage drop would get you over 600 feet at 1 amp, but only about 50 feet at 15 amps.