A method, a system and a computer program product for specifying the source of power and provider of carbon offsets for an electrical device or service. A power supply specification (PSS) utility enables a user or program to specify a preferred blend of power sources and preferred carbon offset provider via a set of programmable requirements and the utility dynamically configures the electrical device or service, based on those requirements. The PSS utility determines the instantaneous power consumption of the device based on the outputs of sensors that measure voltages and currents associated with the operation of the device. The PSS utility compares the device's power consumption with the power from available power generating sources against the set of programmable requirements. When the available power is unable to satisfy the programmable requirements and/or is not sufficient to fully power the device, the PSS utility automatically places the device into a reduced power state. The PSS utility reports information about the device's power consumption to the power supplier.