What size wire when you are 20 from service panel and use 30 amp breaker?

For a 30-amp breaker and a distance of 20 feet from the service panel, you typically should use a minimum of 10-gauge copper wire or 8-gauge aluminum wire. This ensures that the wire can safely handle the current without overheating. Additionally, it's important to consider local electrical codes and any specific requirements for the installation. Always consult a licensed electrician for accurate sizing based on your specific situation.