Earned Value is a term used in the AE industry to indicate how much fee has been earned based upon work performed. If a project has a fee of $1,200 and 18% of the work has been completed the then Earned Value would be 18% of $1,200 or $216.
The million-dollar question is how is the 18% level of completion determined? Usually, it comes from years of experience and looking at what has been produced. Some folks will look at how many hours they believe a project or task is going to take to complete and then compare that to the hours accrued. While this method is not incorrect it does not take into account the variant in productivity levels of workers. If a very efficient worker has been on the job, then more than 18% of the work may have gotten completed, and vice versa for low-efficiency efforts.
On projects that are billed on an hourly basis, it is much simpler to measure the billing value of the hours worked which is the Earned Value. Keep in mind that study after study has shown that fixed-fee contracts produce higher profits than hourly contracts.