Energy Profit Ratio (EPR) is the ratio of the energy content of a fuel relative to the energy needed to obtain the fuel.
EPR = energy content of fuel/energy needed to obtain fuel
The higher the EPR value is for a fuel, the higher the net energy yield and the more valuable the fuel is because more of the energy can be used for other purposes. Conventional oil, coal and natural gas have high EPR values relative to other energy sources, which makes them extremely valuable. Table I provides some reported EPR values. (EPR is called by some EROI-Energy Return On [energy] Investment.)