I have a 240v electric water heater that I am getting rid of (going NG tankless). Can I use the now unused 240v wire that comes from the breaker panel as a 120 volt receptacle so I can have a plug on the wall where the old electric water heater was? The new tankless water heater is going elsewhere in the basement and will have it's own circuit in it's new location.

Thanks.

Yes if the old cable has 3 wires plus ground (i.e. red or black + white + ground). You'll need to buy a box & box connector appropriate for the wire you have, and you may need to put in different breakers to match the rating of whatever plug you install.

On the other hand, if this is in your utility/ work room, you may like having a 240V receptacle there. I have a really nice 240V table saw running off a wire that used to feed the dryer in my basement.

Usually a hot water tank was wired up with -2 with ground. You will have black, white and bare. At the outlet, connect black to brass, white to silver, and bare to green. At the panel, replace the double pole breaker with a single pole one. If the wire is #12 or greater, use a 20 amp breaker. Connect the black wire to it, and connect the white to the neutral bar with the other whites. The ground should have been connected to ground bar before. Leave it as is.

If the cable did have a red wire too, I would just cap both ends with a wire nut.

If it is red, black and ground, Identify Red as neutral(white tape) at both ends, and wire like above.

Thanks for the info. The existing cable is red and black - I can change the breaker, label the red as neutral and go from there.

Thanks again.