A direct current, DC, hybrid solar power supply control system comprising: a power arbiter unit connectable to: a photovoltaic DC power supply wherein an output DC voltage of the photovoltaic DC power supply will vary with variance on incident solar radiation; the power arbiter unit being connectible to the variable DC output of the photovoltaic DC power supply ; and at least one other DC power supply operable at settable voltages; wherein the power arbiter unit includes circuitry to connect the photovoltaic power supply and the at least one other DC power supply and to combine power from the photovoltaic DC power supply and the at least one other DC power supply for DC output, and transition between the photovoltaic DC power supply and the at least one other DC power supply based on the available input power from the photovoltaic DC power supply and the at least one other DC power supply , such that a DC power output from the power arbiter unit will be from the one of the photovoltaic DC power supply and the at least one other DC power supply having a highest operating voltage; and wherein when the photovoltaic DC power supply and the at least one other DC power supply are operating at a same DC output voltage, the DC power output from the power arbiter unit will be combined from the photovoltaic DC power supply and the at least one other DC power supply for uninterrupted transition between the photovoltaic DC power supply and the at least one other DC power supply; and a power controller configured to direct variation of an apparent load applied at the DC output of the power arbiter unit to control DC power drawn by the apparent load to thereby influence the operating voltage of the photovoltaic DC power supply for incident solar radiation and transition between the photovoltaic DC power supply and the one or more at least one other DC power supply . a photovoltaic DC power supply wherein an output DC voltage of the photovoltaic DC power supply will vary with variance on incident solar radiation; the power arbiter unit being connectible to the variable DC output of the photovoltaic DC power supply ; and at least one other DC power supply operable at settable voltages; wherein the power arbiter unit includes circuitry to connect the photovoltaic power supply and the at least one other DC power supply and to combine power from the photovoltaic DC power supply and the at least one other DC power supply for DC output, and transition between the photovoltaic DC power supply and the at least one other DC power supply based on the available input power from the photovoltaic DC power supply and the at least one other DC power supply , such that a DC power output from the power arbiter unit will be from the one of the photovoltaic DC power supply and the at least one other DC power supply having a highest operating voltage; and wherein when the photovoltaic DC power supply and the at least one other DC power supply are operating at a same DC output voltage, the DC power output from the power arbiter unit will be combined from the photovoltaic DC power supply and the at least one other DC power supply for uninterrupted transition between the photovoltaic DC power supply and the at least one other DC power supply; and a power controller configured to direct variation of an apparent load applied at the DC output of the power arbiter unit to control DC power drawn by the apparent load to thereby influence the operating voltage of the photovoltaic DC power supply for incident solar radiation and transition between the photovoltaic DC power supply and the one or more at least one other DC power supply . <EOS>