<p>An electromagnetic (EM) absorber is presented in this work that is utilized not only for absorbing terahertz waves but also for generating ultra-low-power electrical energy from the absorption process. The EM energy absorbed by the absorber is converted into heat energy, which is further utilized here to produce electrical energy via the thermoelectric effect. Thus, the proposed absorber not only provides EM shielding but can also be employed as a thermoelectric energy harvester to support low-power electronic devices. Successful modelling of the terahertz EM absorber-cum-thermoelectric energy harvester leads to sustainable technology development required in today’s era and the near future. The graphene oxide nanomaterial-based EM absorber was modelled to absorb terahertz waves with a reflection coefficient of −62.84&#xa0;dB at 10 THz and transmission coefficient below −40&#xa0;dB from 2 THz to 20 THz, covering almost the entire submillimetre spectrum. In addition, from temperature analysis, it was calculated that after absorbing terahertz waves for approximately 60 s, the surface temperature of the designed absorber increased to 360°C, making it a good thermoelectric energy harvester when coming in contact with a radiative cooler placed at room temperature (29°C). Thus, the proposed absorber-cum-energy harvester structure assists in both EM shielding and ultra-low power generation.</p>