Work out desalination energy requirement instantly with clear inputs, formula shown and shareable results.
Modern seawater reverse osmosis consumes 3-4 kWh per cubic metre of permeate, against a thermodynamic minimum near 1 kWh/m3 at typical seawater salinity and recovery. Brackish water needs 0.5-1.5 kWh/m3. Isobaric energy recovery devices capture concentrate pressure and cut consumption by 25-40%.
Energy consumption
Daily energy (kWh) = permeate volume x specific energy consumption
Energy cost
Cost per m3 = specific energy x electricity price
Because the osmotic pressure of seawater sets a thermodynamic floor. Real plants are already within a factor of three of it, so remaining gains come from pretreatment, pumps and recovery devices rather than the membrane process.
Multi-stage flash and multi-effect distillation consume far more primary energy, typically 10-20 kWh equivalent per cubic metre, and are only competitive where waste or very cheap heat is available.