Injection Molding Energy Requirements

An ab-initio case can be made that injection molding takes more energy than 3D printing, because the mold has to cool between cycles. That means probably 25%-50% less energy efficiency than 3D printing, where you don't have to cool the final object - cooling happens passively.

Now to make 3D printing filament, we have done the heating step 2x: once to produce filament, and once to do the 3D printing., so overall, we are probably 50% less energy efficient than injection molding. More detailed analysis is worthwhile here.