Desalination Energy Requirement Calculator

Work out desalination energy requirement instantly with clear inputs, formula shown and shareable results.

About Desalination Energy Requirement Calculator

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%.

Formulas

Energy consumption

Daily energy (kWh) = permeate volume x specific energy consumption

Energy cost

Cost per m3 = specific energy x electricity price

Worked example

With the default values below, Desalination Energy Requirement Calculator returns Daily Energy Consumption of 35,000.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Permeate Producedminimum 0 m3/day: 10,000 m3/day
Specific Energy Consumptionminimum 0 kWh/m3: 3.5 kWh/m3
Energy Recovery Device Efficiencyaccepts 0–100 %: 95 %
Electricity Priceminimum 0 per kWh: 7 per kWh

Results

Daily Energy Consumption: 35,000.0
Energy Cost Per Cubic Metre: $24.5000
Daily Energy Cost: $245,000.00
Energy Saved By Recovery Device: 805.6

Step by step

1Values used
2Energy consumption
3Energy cost
4Daily Energy Consumption= 35,000.0
5Energy Cost Per Cubic Metre= 24.5000
6Daily Energy Cost= 245,000.00
7Energy Saved By Recovery Device= 805.6

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why can specific energy not fall much further?

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.

Does thermal desalination compare?

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.