Under the Project Schedule management knowledge area, there is a specific process called Develop Project schedule. Under this process, we have Resource Optimization Techniques and these are Resource Levelling and Resource Smoothing. In this blog, I am addressing differences between Resource Levelling and Resource Smoothing.

Now, as both of these techniques are resource optimization techniques so their primary focus is to allocate resources in such a way to bring maximum output effectively. Due to this reason, Project Management Professional (PMP)® Certification test-takers generally gets confused between these two terms.

Let us begin with an exploration of these techniques one by one:

What is Resource leveling?

“A technique in which start and finish dates are adjusted based on resource constraints with the goal of balancing the demand for resources with the available supply.” – PMBOK® Guide Sixth Edition

We can use Resource Levelling both for human and material resources. We need this tool when shared or critical resources are available only at:

  • defined times,
  • in limited quantities, or
  • over-allocated

Like when we assign a resource to two or more activities at the same time, it is over-allocation. A resource cannot work beyond 8 hours in a day. Here, it needs resource-leveling. We need to take care of available supply and based on that we can adjust work duration.

Let’s take another resource leveling example:

Only one resource can do a given activity. If that resource is occupied doing another work on the critical path, the path itself needs to change to include that dependency.
We can say that, if there is a need for Resource Levelling due to resource constraints, we have to go with this resource optimization tool. As a result, it may bring a big change in the project schedule because we have to level it.

Let’s see how:

We do not have more than 45 hours a week to our schedule. Applying this resource constraint may result in a change of project schedule dependencies. And it may result in a change in project duration. In the image above when we applied 45 hours constraint to a 7-week project, then it became a 9-week project schedule.

In essence, resource constraints drive the resource levelling.

Now the question is how to identify that there is a resource constraint?

The primary source is the network diagram. When we create a network diagram, we mainly take care of dependencies (mandatory or discretionary) between activities. The constraints become visible when we assign resources to these activities. Resource Levelling may change the critical path of the network diagram. The reason lies in the change in the duration of the project schedule. We can see that change in the critical path is very interesting in this process. And to get this process, I recommend watching the video available at the end of the blog.

Here you can see some disadvantages also. Let’s get the answer to the question –What are the disadvantages of resource Levelling?

There are many disadvantages as we have to live with constraints. We may need to delay certain tasks due to over-allocation or due to the scarcity of resources.

Ok, let’s explore the answer to another compelling question – What are the advantages of resource leveling?

Resource leveling takes care of the bad allocation of resources. It gives a clear picture of what can be done within available resource constraints.

Now come to the next Resource Optimization Tool – Resource Smoothing

“A technique that adjusts the activities of a schedule model such that the requirements for resources on the project do not exceed certain predefined resource limits.”– PMBOK® Guide Sixth Edition.

In simple words, let’s discuss what is Resource Smoothing?

After applying resource-leveling we have a resource-constrained schedule. But we may still need the desired level of allocation in the project plan. Here, the question is why? We love to keep things well managed. We need some breathing space. Each day activities cannot be assigned for 8 hours in the day.

Let’s say our desired level of allocation per week is 38 hours. Now by doing Resource Smoothing; we try to adjust activities in such a way that we achieve this desired level of resource allocation. We may not be able to do it for all the weeks since we do not think of changing the project duration here. So we do it only wherever slack is available. We are not aiming to change the project duration; we smoothed the project schedule by playing around the free and total float.

Let’s summarize differences between Resource Leveling and Resource Smoothing

Resource leveling Resource Smoothing
It applies the resource constraints to the project and may result in a change in project duration. We apply resource smoothing after doing resource-leveling.
Since we need to first accommodate the resource constraints before we can optimize it.
Here we make use of slack, and will not result in a change of project duration. Because the total allocation of a certain resource remains the same.
Resource Leveling is primarily driven by resource constraints like you do not have more than 45 hours of the given resource for a week. Resource smoothing is more to do with desired limits like we do have 45 hours available for a given resource but we wish that we allocate 38 hours per week so we have some breathing space.
The allocation limits identified in resource leveling must be applied. The desired limit identified in resource smoothing may not be applied in some cases, if we do not have slack. It is optimized within the float boundaries
When Resource Leveling changes the project dates, may also change the critical path, since constraints drive it. Resource smoothing will not change the critical path; it tries to make the best use of slack.

I have also posted a forum thread to communicate the difference between Resource leveling and Resource Smoothing:

Resource LevelingI’m sure I have answered all your questions on the differences between resource leveling and resource smoothing.

You may also like to watch a video presentation on differences between resource leveling and resource smoothing.

You can join the discussion on the same in our Forum. You can also log in to our YouTube channel watch the video on the same.

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