Greece confronts intensifying water scarcity driven by population growth, urbanization, tourism, and climate variability, despite its extensive coastline. Traditional sources are strained, with agriculture consuming ~80% of withdrawals (surface water ~38%, groundwater ~62%). Desalination, predominantly reverse osmosis (RO), offers a mature solution, already meeting 30–95% of domestic needs in Aegean islands, but its energy intensity challenge sustainability within the water–energy–food nexus. This study presents a geospatial framework to assess energy requirements for a hypothetical scenario in which seawater desalination fully supplies domestic water demand in Greece. High-resolution GIS data, WorldPop population grids, and hydrological networks enable estimation of daily demand (173 L/capita/day) and energy decomposition: desalination (SEC = 5 kWh/m3 SWRO), elevation pumping plus residual pressure (15 m head), and frictional losses. The hypothetical pipelines follow reverse natural drainage paths for realistic routing. Results highlight substantial spatial disparities: inland cities face significantly higher and more uniform energy costs (Ioannina: mean dynamic head 8.3 kWh/m3, ~43% higher than the coastal reference of Athens at 5.8 kWh/m3), driven by elevation and distance; coastal centres show lower means but greater variability (Athens: highest total ~3.35 GWh/day). In summary, fully supplying domestic water demand via desalination would necessitate an additional ~8% of the country’s total electricity consumption. Findings affirm desalination’s potential for coastal/island supply while revealing energy barriers inland.
