Enter direct costs as quantity × rate by discipline, or add common items from the library dropdown. Each line carries:

• Basis: how the number was derived (quoted through to judgment). It seeds the line's contingency and, in probabilistic mode, the width of its cost distribution.
• Source: the reference (quote, past project, price book). Unreferenced lines lower the quality score.

Markups cascade: P&G on direct, margin on (direct + P&G), then design, commissioning, MSQA and client costs on the construction total. Choose the contingency method in Settings: deterministic, line-item or probabilistic.

Remove a row with ✕, then click Remove to confirm. There is no undo.

OPEX is built from plant drivers, not typed totals:

• Chemicals: dose (mg/L) × flow × supply cost. For liquids priced per litre, set the product SG.
• Power: installed kW × load factor × run hours × tariff.
• Consumables: replacements per year from item life (hours) against operating hours (Settings).
• Maintenance: % of the matching CAPEX discipline subtotal.

Use the library dropdowns to add common items quickly, or add your own.

A cheaper plant to build can cost more to own. This tab discounts everything the option will cost over its life into one comparable figure, so options are judged on total cost, not just CAPEX.

NPV (Net Present Value)

Today's value of all future costs: CAPEX now plus every year of OPEX and replacements, each pulled back to present value. Lower is cheaper overall.

Discount rate (real)

Converts future dollars to today's dollars. "Real" means inflation is stripped out, so all figures are in today's money and don't need an inflation guess.

Real vs nominal

Real = today's money (used for the NPV comparison). Nominal = actual future dollars including inflation (the escalated outturn CAPEX shown below is nominal, the number to carry into a budget).

Renewals: why they're here

Plant components wear out and are replaced on a cycle well before the plant itself: UV lamps, membranes, filter media, mid-life mechanical refurbishment. These are real, repeating capital costs. Leaving them out flatters options that rely on short-lived kit (for example membranes) and understates their true life-cycle cost.

EAC (Equivalent Annual Cost)

The NPV spread evenly across every year of the horizon: a single "$/year to own" figure that's easy to compare across options with different lives.

Unit cost ($/m³)

EAC divided by annual volume treated: the cost of producing a cubic metre of water. The number operators and councils feel most directly.

Every option is recalculated and lined up side by side. The lowest-NPV option is marked, but read it alongside CAPEX affordability, unit cost and class. A lower NPV built on a higher-uncertainty class is not a like-for-like win.

Choose which sections to include (for the active option), then:

• PDF opens your browser's print dialog: choose "Save as PDF". Turn off "Headers and footers" for a clean page.
• CSV downloads line items and summaries for a spreadsheet.
• Save (JSON) writes the full multi-option estimate to a file. Load restores it.