System Information
Operating system: Win 7
Graphics card: R7 360

Blender Version
Broken: (example: 2.80, edbf15d3c044, master, 2018-11-28, as found on the splash screen)
Worked: (optional)

Short description of error
Upon creating a short animation I learned emissions could achieve the same lighting I was going for so I created a new file (See "NEW FILE") and did the same animation (a short 15 second spinning globe with transparency) using emissions and rendered it. The file came out 4GB in size.

Astounded I checked all the settings in my old save (See "OLD FILE") to see if they both had the exact same settings and then rendered it again, only a few hundred MB. So I redid the same animation in the old file with emissions and rendered it again, this time the file size was smaller than the last render from this file (OLD FILE)

In short summary, I have the same animation in 2 save files with the same render settings, when I render from one, it's a few hundred MB when I render from the other or create a new project with those same settings, it comes out a 4GB file.

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).

Select a render destination of the attached .blend files and click render.