Why would my outlet read 20V in a 120V AC line?

Two things:

1) Loose Neutral connection.
2) What type meter are you using and is it set to the correct scale?`

An open neutral of a multi-wire (shared neutral) branch circuit would cause this reading, along with blowing up anything plugged into either circuit.

Don asked a good question, exactly what test instrument are you using to see 20 volts? Many digital volt meters would read induced voltage, which a 20 volt reading could indicate simply no voltage.

HA! I read that as "220V". Damn my old eyes.

I live in a glass house, so no comments from me on your age,.