Some confusion exists surrounding this topic and the simplest way to explain it is ordination is a “laying of the hands,” or ceremony that empowers an individual to proceed with a life that centers on ministry. Installation, on the other hand, situates an individual at a specific church or in a specific role at a church. Installation usually follows ordination. According to a Google book entitled What is Presbyterian Law as Defined by the Church Courts: “Ordination inducts into the office;…installation gives him authority to exercise his office over a particular church.”
In an article for SBC Impact, author David Rogers writes: “In traditional Baptist practice, there is a three-fold recognition of God’s call on the life of an individual, and commendation to ministry: first, license to preach; next, ordination; and next, installation into a specific ministry role.”
There is scriptural evidence that speaks generally to installation as well, according to Rogers. “InActs 6:1-7, seven men (commonly regarded as the first deacons) were chosen by the members of the Jerusalem church to oversee the daily distribution of food. The apostles prayed for them, and laid their hands on them, apparently commending them publicly to this specific task. In Matthew 10; Mark 3:13-19, 6:7-13; Luke 6:12-16, and 9:1-6, Jesus Himself personally commended the twelve apostles to specific ministry tasks, as well as appointed them to the specific ministry “role” they were to carry out in the Church. Judas was later disqualified from his appointment after his betrayal of Jesus, and subsequent death. In Acts 1:15-26, we learn that Matthias was named to take his place through the process agreed upon by the other eleven.”
While installation is certainly a modern ceremony, you can trace its roots back to the New Testament. The idea of being charged with a ministerial office or faithful responsibility is woven throughout biblical scripture.
This YouTube video shows a beautiful installation service ceremony for a newly appointed pastor.