Acceleration does not waste energy (other than speed related things like wind resistance). This is a myth that is perpetuated without merit, but probably because it's typically associated with overall aggressive driving, which implies bad braking habits.

Max efficiency is typically near peak torque for internal combustion engines [0]. For EV's, electric motors are actually most efficient at higher RPMs [1].

Fuel efficiency can be measured by breaking habits alone.

Edit: sources:

[0] https://i.stack.imgur.com/RE4SM.png

[1] https://qph.fs.quoracdn.net/main-qimg-fcf541de83bd871b9ba92d...