I came across a battery-electric mini excavator on the internet, and it appears to still use hydraulics to power the arm. That got me wondering why they didn’t just use electric motors (with the appropriate gearing) instead? Is it cost? More efficient use of energy? Reusing parts from other gas models? Weight reduction at the end of the arm? Something else?

I’m not aware of any industrial robot arms that use hydraulic actuators, so there are obviously advantages for electric motors too. How does a mechanical engineer think about when each type of actuator is the correct choice for a particular design?