Variance at Completion (VAC) is a projection of the budget surplus or deficit. It is expressed as the difference of the Budget at Completion (BAC) to the Estimate At Completion (EAC). This project management concept is the difference between the expected or baseline cost of the project and the current estimated cost.
Interpreting the result of the Variance At Completion (VAC) is simple. For instance, if the VAC is a positive integer, it is a clear sign that the project is under budget. If the result is negative, then it means that the project will be over budget. The greater the distance between the VAC value and zero, the higher the margin of error in the budget calculations. Thus, it is ideal for the VAC value to approach zero which means that the estimate is accurate. It also indicates that the project manager need not plan for any contingencies.
This project management concept describes projection. It has a similar function with the Cost Variance formula but it is used on a macroscopic level thus it is used as a status snapshot by many project managers.
This term is defined in the 5th edition of the PMBOK.