The extent and pace of the transition from our current fossil fuel-based economy to one based on renewable energy will strongly depend on the availability of bulk energy storage solutions. Herein, we investigate one such candidate technology, using chemical precursors which are inexpensive, abundant, and widely available, specifically cement, water, and carbon black. The energy storage capacity of these carbon-cement supercapacitors is shown to be an intensive quantity, and their high rate capability exhibits self-similarity. These properties point to the opportunity for employing these structural concrete-like supercapacitors for bulk energy storage in both residential and industrial applications ranging from energy autarkic shelters and self-charging roads for electric vehicles, to intermittent energy storage for wind turbines.