As a FDM printer owner, it does use quite a bit of energy.
My ender 3 uses 0.125kWh[0] with 200C extrusion (PLA) and 60C bed, but making a durable children spork can take hours.
my personnal guess: by plastic mass, FDM is probably way less efficient energy wise than injection molding for the same mass of plastic, since meltic plastic a tiny volume at a time must have more losses than having a big amount heated at once.