Desalination & Membrane Water Treatment Equipment worked example

Water Production Cost at 58% share of variable cost included in scope: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop share of variable cost included in scope to 58%, then walk the calculation through step by step. Estimate cost to produce permeate or treated water by combining production volume, variable treatment cost, included cost scope, and fixed skid or plant charges.

The inputs for this scenario

  • Treated water volume produced: 100 m³ (held at the documented default)
  • Variable cost per m³ produced: 45 $ / m³ (held at the documented default)
  • Share of variable cost included in scope: 58 % (the input this scenario stresses; the baseline uses 80)
  • Fixed plant or skid overhead: 250 $ (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Included variable production cost = treated water produced × variable production cost × production cost scope included.
  • Total water production cost works out to 2,860 $ at these inputs, and this is the headline figure for the scenario.
  • Water production cost per m³ works out to 28.6 $ / piece at these inputs.
  • Included variable production cost works out to 2,610 $ at these inputs.
  • Fixed plant or skid cost works out to 250 $ at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where share of variable cost included in scope sits at 80% and the headline result is 3,850 $, this scenario comes in 25.71% below the baseline at 2,860 $.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to share of variable cost included in scope, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. This is an operating-cost rollup, not a full levelized cost of water — it omits the time value of capital, financing, and membrane replacement reserves unless you bake them into the inputs.

Results at a glance

  • Total water production cost: 2,860 $ (headline result)
  • Water production cost per m³: 28.6 $ / piece
  • Included variable production cost: 2,610 $
  • Fixed plant or skid cost: 250 $

Run it with your numbers

  • To rerun this with your own numbers, open the live Water Production Cost calculator, set share of variable cost included in scope to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.