How will future urbanization and climate change reshape the global electricity generation potential of rooftop photovoltaics?

Rooftop solar panels need no new land, which makes them a rare clean-energy option for crowded cities and off-grid communities. But a study published in The Innovation Geoscience suggests that the technology's room to grow may fall short of what a hungry, urbanizing world will demand of it. The researchers combined four socioeconomic-climate scenarios (SSP-RCP) with electricity demand projections to track rooftop photovoltaic (RPV) potential from 2015 to 2100. Their baseline: in 2015, global RPV technical potential stood at 23.9 petawatt-hours, about 3.3 megawatt-hours per person. The distribution was starkly uneven—high-income countries averaged 8.3 MWh per capita, more than double upper-middle-income countries (3.1) and roughly four times lower-middle-income (1.5) and low-income countries (2.1). Still, more than 80% of countries had technical potential exceeding national electricity demand. Through 2100, the models project global RPV potential growing 13–20%, driven mainly by urban expansion. Climate change cuts both ways: under low-emissions scenarios it adds 2–3% to potential, but under high-emissions scenarios it subtracts 3–4%—erasing nearly one-fifth of the gains from rooftop expansion. Low- and lower-middle-income countries, urbanizing fastest, gain more than 15% in every scenario, yet in high-emissions futures climate losses consume roughly 20% of their expansion benefits. The deeper problem is arithmetic. Cities are densifying, so roof area per person is shrinking even as total roof area grows; per capita potential and population size are strongly negatively correlated. Meanwhile, global electricity demand is projected to reach 2.8–4.6 times current levels by 2100, led by the very countries where per capita rooftop potential is falling hardest. The result: RPVs' maximum feasible share of global electricity could drop from 117% today—when roofs alone could in principle cover the world's power needs—to 30–47% by 2100. The squeeze is sharpest in developing countries, particularly the least developed. Many are projected to shift from supply-demand surpluses above 200% to deficits larger than those of wealthier countries—despite gaining total potential—because population density outruns roof construction. In low-income countries, per capita potential declines under every scenario, leaving them with the lowest per-person levels after mid-century. The authors frame this as an equity issue, not just an energy forecast. Countries that rely on rooftop solar for clean electricity access stand to lose the most ground exactly when demand grows fastest. Their prescription: embed climate mitigation into urban planning and accelerate international technology cooperation, so the disproportionate impacts do not harden into a two-tier energy transition.