A method and apparatus for controlling power consumption of a facility, building or simply a collection of one or more devices, by load shedding when power consumption is above, or is predicted to be above, a preselected setpoint, but only if electrical power on the spot market cannot be purchased at or below a preselected price. The apparatus and method of the invention optimizes power usage by taking advantage of the buying of electricity as a commodity on the spot market. As a further aspect of the invention, in the situation of a supermarket for example, which refrigerates food products, artificial product core temperature sensors or direct insertion product sensors can be used to continuously monitor the refrigerated temperature of perishable products. A controller would constantly monitor these temperatures to allow a precise load shedding routine to be implemented.