A method includes: calculating a load prediction arising from an power consumption entity over a prospective time period; calculating a predicted off-grid power supply from an off-grid power supply; minimizing, for a respective time interval, a calculated amount of electrical-power to import from a power grid, in accordance with output from a cost function; and, for at least one interval, importing, from the power grid, the corresponding calculated amount of electrical-power corresponding to the at least one interval. The cost function uses: (i) a multi-component time of use tariff schedule associated with the power grid that includes a first power rate during a prospective time period and second power rate during a second time period, (ii) the load prediction over the prospective time period, (iii) the predicted off-grid electrical-power supply over the prospective time period, (iv) a state of a rechargeable battery.