Software-Defined Metamaterials (SDMs) are envisioned to enable the control of electromagnetic waves at an unprecedented scale. Various SDM applications will require downlink and broadcast-based transmission of control packets from a powered transmitter to energy harvesting nanonodes. The nanonode’s communication system is anticipated to be a bottleneck for such nanonetworks, hence an accurate modeling of its energy consumption is needed. Time-Spread ON-OFF Keying (TS-OOK) is a prevailing scheme for nanocommunication in the Terahertz (THz) frequencies, with short pulses representing logical 1s and silences (0s). In the energy modeling of this scheme, a certain energy is usually attributed to the transmission or reception of the pulses, without considering the energy consumed in idling. To enable more realistic modeling, we propose an energy consumption model that additionally accounts for the idling energy. In a scenario relevant for numerous SDM applications, we demonstrate that the idling energy consumption is substantial and cannot be disregarded. To reduce the idling energy consumption, we propose a new duty cycle for the receiving nanonodes. Assuming frequent packet repetitions on the transmit side, the proposed duty cycle utilizes short wake-ups of the receiving nanonodes. Additionally, we propose two algorithms for deciding when these wake-ups should be performed. For two energy harvesting options expected to be utilized in prominent SDM applications, we show that, in case the proposed duty cycle is utilized, three orders of magnitude higher idling energy consumption can be tolerated compared to the baseline. Finally, we demonstrate encouraging performance of the proposed algorithms in increasing the communication reliability.