Efficacious Grace is produced by God and revealed by the Holy Spirit through (in) Jesus Christ. Efficacious means: producing a desired effect, and grace means: everything that God did/does for mankind based on the Cross-work of His Son. Therefore, efficacious grace means: God produces the exact effect of His plan while we are yet in sins. The Holy Spirit makes the faith of spiritually dead unbelievers effective for salvation. The unbeliever is totally helpless until God opens the eye of faith. This is grace (Romans 5:8). Reference also “Divine Decrees/Election”
Efficacious grace is the ministry of the Holy Spirit in making the faith of the spiritually dead person effective for eternal salvation. Common grace and efficacious grace emphasizes the total helplessness of the spiritually dead (unsaved) person. No matter what a spiritually dead person can perform (physical things), it is not salvation, which is a spiritual thing.
If you are not a spiritual entity, you can not perform anything spiritual. Therefore, only God can perform salvation. Salvation comes only through Jesus Christ. Faith is a non-meritorious (unearned) decision to believe in the salvation accomplishments of Jesus Christ on the cross, when He paid our sin debt. The Holy Spirit makes our faith effective by faith alone in Christ alone (2 Corinthians 6:1-2).