On-site fuel cells, mostly solid-oxide, installed behind the meter to power racks directly and skip the multi-year grid-interconnection queue. Tightens when data-center primary-power demand outpaces the fuel-cell systems that vendors can build and deploy.
A sustained tight read means demand for behind-the-meter fuel-cell power is running ahead of the systems vendors can build and deploy, so contracted orders queue against installed manufacturing output. The read is vendor revenue at the largest fuel-cell suppliers, a proxy: it tracks how hard order flow is pulling on that capacity, not the number of energized systems. Relief arrives only as vendor manufacturing capacity expands and new systems ship, over quarters rather than a single order cycle.