What Does Desalinated Water Really Cost per Cubic Metre?
“What does a cubic metre of desalinated water cost?” It is the most frequently asked question we get, and the most often answered vaguely. The industry figure is roughly USD 0.55–1.00/m³, and the spread is wide because cost depends heavily on plant size, electricity tariff and feed water quality. Break the number open and you can see where your project will land.
1. Five components make up the cost
Electricity — 40–55%
The largest single item. RO specific energy is 3–4 kWh/m³ with energy recovery, 5–8 kWh/m³ without. At USD 0.10/kWh that is USD 0.30–0.80/m³. Over ten years, the difference between fitting and omitting energy recovery is roughly the price of another machine.
Membranes and cartridges — 15–25%
Seawater membranes last 3–5 years; amortised, that is USD 0.06–0.13/m³. Cartridges are changed every 1–3 months and multimedia media topped up every 3–5 years. This line is driven almost entirely by feed turbidity and how well pretreatment is designed.
Chemicals — 5–10%
Antiscalant, biocide and reducing agent, budget USD 0.03–0.07/m³. Do not economise here: halve the dose and you may halve membrane life.
Labour and maintenance — 10–20%
Small plants can run unattended with periodic inspection; large plants need full-time operators. The smaller the plant, the higher labour cost per cubic metre.
Depreciation and capital charge — 15–25%
Straight-line over a 10–15 year equipment life, plus civil works, intake and outfall.
2. Realistic ranges by plant size
| Capacity | Specific energy | All-in water cost | Comment |
|---|---|---|---|
| 10 m³/d (marine / single island) | 3.5–5 kWh/m³ | USD 0.85–1.70/m³ | Depreciation and labour spread thin; highest unit cost |
| 100 m³/d (village / small factory) | 3–4.5 kWh/m³ | USD 0.65–1.00/m³ | The sweet spot for value |
| 1,000 m³/d and above (park / municipal) | 3–3.8 kWh/m³ | USD 0.55–0.85/m³ | Clear scale effect; better power tariff negotiation |
For reference, long-distance water transfer to China's coastal cities costs roughly USD 0.9–1.1/m³. In other words, RO desalination above a few hundred cubic metres a day is already competitive with moving water inland.
3. Three numbers that matter more than the equipment price
The power tariff. Electricity is nearly half of the total, so dropping the tariff from USD 0.10 to USD 0.07/kWh removes USD 0.09–0.21/m³. Off-peak operation with storage, or on-site solar, pays back quickly.
Recovery ratio. Raising recovery from 30% to 40% cuts intake volume and pretreatment load, but increases concentration polarisation and scaling risk. The balance point must be calculated from actual salinity and temperature, not guessed.
Actual membrane life. A membrane designed for five years and replaced after two adds well over USD 0.07/m³ immediately. Around 90% of membrane life is determined by pretreatment and correct CIP practice.
4. Three ways to cut cost, ranked
- Fit energy recovery. One-off capital, 30–40% off specific energy, payback typically 1–3 years. The best-value money in the whole plant.
- Build pretreatment properly. Multimedia plus ultrafiltration plus antiscalant looks expensive but is the most effective way to extend membrane life.
- Add automatic control and remote monitoring. Fewer inspection rounds, and no more running the plant at abnormal pressure until the membranes are destroyed.
Shenzhen Duruofei Technology Co., Ltd. quotes the equipment list and an operating cost estimate together, so the customer sees the ten-year electricity and membrane bill before signing. Cheap equipment does not mean cheap water — that is the single point we most want to make clear.
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