A method and apparatus for generating power in a demand responsive manner is disclosed. The apparatus includes a controller monitoring power demand conditions to determine activation of an energy delivery system. The energy delivery system responds to the controller by providing rotational energy through release of a power transfer and brake unit, which permits descent of a suspended mass as a means for providing rotational energy. The rotational energy is transferred to a generator through a combining gear box and transmission communicating with the energy delivery system. The controller modulates the power transfer and brake unit to maintain the rate at which the mass descends to assure that a predetermined, substantially constant RPM of the generator is maintained for generation of power by steps for generating power.