The mass and energy-capital conservation equations are employed to study the time evolution of mass and price of non-renewable energy resources, extracted and sold to the market, in case of no-accumulation and no-depletion; i.e. when the resources are extracted and sold to the market at the same mass flow rate. The Hotelling rule for non-renewable resources, i.e. an exponential increase of the price at the rate of the current interest multiplied the time, is shown to be a special case of the general energy-capital conservation equation when the mass flow rate of extracted resources is unity. The mass and energy-capital conservation equations are solved jointly to investigated the time evolution of the extracted resources. The parameter PIFE...