Before addressing when to use a Statement of Work (SOW) or a Performance Work Statement (PWS), it is good to discuss what they are and what the differences are. The FAR does not define SOW, but it has been described as a document which describes the work that the contractor needs to accomplish, and directs the contractor how to accomplish the work. A PWS on the other hand, is defined in the FAR. According to FAR 2.101, “Performance Work Statement means a statement of work for performance-based acquisitions that describes the required results in clear, specific and objective terms with measurable outcomes.” In other words, a PWS says what needs to be done, but does not say how the work is to be accomplished. This allows the contractor to be innovative in achieving the outcomes required by the PWS.
To illustrate the differences, let’s look at an example. Let’s say that we have a requirement for grounds maintenance. If we were to use a SOW, we would probably say that the grass must be mowed once a week and that the grass needs to be watered every other day. In order for the contractor to be successful, they would have to mow once a week, regardless if the grass was too tall or not. Also, the grass would need to be watered regardless if it had rained lately or not. If we were to put this requirement into a PWS, we might say that the grass has to be 3 inches tall plus or minus 1 inch and that the ground must have a certain level of hydration. In this case, the contractor can be innovative and measure the grass on a regular basis and only mow the grass when it is approaching 3 inches. They would also measure the hydration and water only when the ground needs water. One can see that using a PWS can allow the contractor to think and only work when needed to meet the measurable objectives.
Now that we understand the differences between a SOW and a PWS, we need to decide which one to use in a certain acquisition. The decision as to which one to use gets down to the requirement. If there is a specific procedure which needs to be done to incorporate into a system or to fit into other services, then a SOW might be appropriate. In this case, the contractor must follow the prescribed procedure and cannot deviate. If there is not a specific procedure that must be followed, the use of a PWS will usually yield better results and often at a lower cost.