A 240v breaker looks like 2 breakers held together by the switch handle.
If a 240v breaker says 20-20 it is 20 amps at 240v. This is plenty for any current Chevrolet Volt, which maxes out at 16 amps.
But if you anticipate getting another EV in the future, go with the 30-30 breaker. This will support 30a x 80% = 24 amps of continuous duty charging. Make sure it's 10 gauge or thicker wire.
To go Whole Hog, pull either breaker, replace with a 50-50 240v breaker and put in a 14-50R outlet using 6 gauge wire. This will support 40a charging for Teslas and 32a for Bolt EVs.
NOTE: It sounds like you should consult an electrician.
If a 240v breaker says 20-20 it is 20 amps at 240v. This is plenty for any current Chevrolet Volt, which maxes out at 16 amps.
But if you anticipate getting another EV in the future, go with the 30-30 breaker. This will support 30a x 80% = 24 amps of continuous duty charging. Make sure it's 10 gauge or thicker wire.
To go Whole Hog, pull either breaker, replace with a 50-50 240v breaker and put in a 14-50R outlet using 6 gauge wire. This will support 40a charging for Teslas and 32a for Bolt EVs.
NOTE: It sounds like you should consult an electrician.