EROI

EROI stands for "energy return on investment". Even in a world without money, EROI would still matter just as much.

Definition: EROI = energy_returned / energy_invested

For energy sources

EROI is an essential factor in determining whether an energy source is viable or not. The EROI has to be a lot greater than 1 (otherwise it would never "break even").

For energy storage

The EROI of any energy storage will always be less than 1, but the hope is to get it high as possible.

To calculate it:

energy_invested should include a few things:

• the energy it takes to manufacture or construct the energy storage(...)( This could include the energy needed to mine the materials. Or not. It's fine either way - but any estimate should specify whether or not this is included. )
• the energy used during its operation (charging)
• the energy it takes to recycle or dismantle the energy storage at its end-of-life

energy_returned should include:

• the energy obtained during its operation (discharging)

For batteries with a lifespan defined by a finite number of charge/discharge cycles:

energy_invested = capacity*lifespan_cycles/charge_discharge_efficiency + energy_in_manufacturing + energy_in_recycling
energy_returned = capacity*lifespan_cycles