Here’s what seawater desalination actually costs in 2026, before anything else:

• Portable / marine (100–500 GPD): $3,000–$15,000
• Small commercial (1,000–5,000 GPD): $15,000–$60,000
• Mid-size industrial (10,000–50,000 GPD): $60,000–$350,000
• Large industrial (100,000+ GPD): $500,000–$5,000,000+

Those ranges are wide because seawater desalination cost is highly site-specific. Feed water salinity, required output quality, local energy prices, pre-treatment needs, and whether the system needs to be containerized for remote deployment all move the number.

What Drives Seawater Desalination System Cost

Feed Water Salinity

Ocean water typically runs 32,000–38,000 ppm TDS. Brackish water runs 1,000–10,000 ppm. Seawater RO (SWRO) requires operating pressures of 800–1,200 psi. Brackish water RO (BWRO) operates at 100–400 psi. Higher operating pressure means heavier pressure vessels, more powerful pumps, and more energy — all of which add cost.

Required Output TDS

Drinking water requires less than 500 ppm TDS. Industrial applications — pharmaceutical, semiconductor, power generation — may require TDS below 10 ppm, which typically means a second-pass RO system. A two-pass system can cost 40–60% more than a single-pass system at the same flow rate.

Pre-Treatment Complexity

Ocean water is biologically active and contains suspended solids, algae, and seasonal turbidity variation. Pre-treatment for SWRO typically requires multimedia filtration, ultrafiltration (UF) membranes, and chemical dosing. In regions with high biological activity, the pre-treatment system can represent 20–25% of total project cost.

Energy Recovery

On large SWRO systems, energy recovery devices (ERDs) — pressure exchangers or turbochargers — capture energy from the high-pressure reject stream and transfer it back to the feed water. ERDs reduce energy consumption by 30–50% on systems above roughly 10,000 GPD. The device itself adds $15,000–$200,000 to equipment cost, but payback is typically 1–3 years.

Cost Breakdown by System Component

Component	% of System Cost	Notes
High-pressure pump	15–25%	Largest single component cost; multistage centrifugal or positive displacement depending on flow rate
RO membranes	20–30%	SWRO membranes (e.g., FILMTEC SW30XHR) cost more per element than BWRO membranes; replace every 3–7 years
Pressure vessels	10–15%	Must be rated for 1,000+ psi for SWRO; fiberglass composite standard, stainless steel for harsh environments
Pre-treatment (filtration, chemicals)	15–20%	Higher for surface seawater with biological loading; lower for clean offshore intakes
Controls and instrumentation	10–15%	PLC-based control with remote monitoring standard on commercial and industrial systems
Frame and housing	5–10%	Containerized housing adds cost but enables rapid deployment
Installation	10–20% of equipment cost	Varies widely by site — offshore and island installations significantly higher

Operating Cost: The Number That Matters Long-Term

Energy Consumption

Seawater RO requires 3–6 kWh per cubic meter of product water produced (with energy recovery; 8–15 kWh/m³ without). Brackish water RO typically consumes 0.5–1.5 kWh/m³ — a 4–10x difference.

At $0.12/kWh (US commercial average):

• 10,000 GPD SWRO without ERD: approximately $110–$220/day
• 10,000 GPD SWRO with ERD: approximately $55–$110/day
• 100,000 GPD SWRO with ERD: approximately $550–$1,100/day

Over a 10-year operating life, energy cost for a 10,000 GPD system adds up to $200,000–$800,000 — often more than the equipment cost. Systems in regions with high electricity rates should prioritize energy recovery and high-efficiency pump selection even when it increases upfront cost.

Membrane Replacement

SWRO membranes last 3–7 years under good operating conditions. A 10,000 GPD system might use 20–30 membrane elements at $200–$350 each. Replacement every 5 years: $4,000–$10,500 per cycle.

Seawater RO vs. Brackish RO vs. Municipal RO

Parameter	Seawater RO (SWRO)	Brackish Water RO (BWRO)	Municipal / Low-TDS RO
Typical feed TDS	32,000–42,000 ppm	1,000–10,000 ppm	100–1,000 ppm
Operating pressure	800–1,200 psi	100–400 psi	50–150 psi
Energy use	3–6 kWh/m³ (with ERD)	0.5–1.5 kWh/m³	0.2–0.5 kWh/m³
Typical TDS rejection	99–99.8%	95–99%	90–98%
Membrane type	FILMTEC SW30XHR or equivalent	FILMTEC BW30 or equivalent	Low-pressure RO or NF elements
Recovery rate	35–50%	60–80%	75–85%

Applications

• Island communities and coastal municipalities: Where freshwater supply is limited or aquifers are at risk of saltwater intrusion, SWRO is increasingly the primary water supply source.
• Coastal hotels and resorts: High-end resort properties in water-scarce coastal regions often run their own SWRO systems to achieve water independence.
• Offshore platforms and vessels: Oil and gas platforms, research vessels, and large commercial ships use compact SWRO watermakers for crew water supply.
• Marine and recreational: Long-range sailing and motor yachts carry compact SWRO watermakers (100–500 GPD) for offshore passages.
• Emergency and disaster response: Mobile containerized SWRO units are deployed after natural disasters to coastal communities that have lost water infrastructure.

AMPAC USA Seawater Desalination Systems

AMPAC USA has manufactured seawater RO systems in Pomona, California since 1993. The product line spans from 100 GPD marine watermakers to 250,000 GPD industrial SWRO systems. Every system ships factory-tested with documented flow rate and rejection performance. FILMTEC SW30-series membranes are standard across the SWRO line — the same membranes used in large municipal desalination plants worldwide.

Systems are available as skid-mounted, trailer-mounted, or ISO-containerized configurations for rapid deployment to remote sites. Custom engineering is available for non-standard feed water chemistry or site-specific installation requirements.