Solar photovoltaic (PV) and wind energy are now the most scalable and cost-effective electricity sources. However, their weather-dependent variability raises concerns about their ability to provide reliable, continuous power. The concept of firm power—the ability to meet demand 24/7/365—is central to addressing this challenge. Research from IEA PVPS Task 16 shows that PV and wind can deliver firm power cost-effectively when combined with battery energy storage systems (BESS), dynamic curtailment (aka implicit storage), and a small share of dispatchable thermal generation using GHG-free e-fuels. This paper quantifies how the cost of firm PV/wind power varies with the geographic scale of the generation footprint across the continental U.S., assuming a flat baseload and 5% e-fuel flexibility. Results show that localized, self-contained firm power systems within areas smaller than 50,000 km² are economically viable, with projected 2050 levelized costs ranging from 4.25 to 6.25 ¢/kWh ─ challenging the assumption that large-scale transmission is essential for reliable renewable power. The study also explores optimal PV/wind mixes, storage requirements, and how these evolve with footprint size.
Remund et al. (Sun,) studied this question.