The dynamic cost comparison calculation determines the preferred alternative for all planning in the water management sector. Data are imported into the dynamic cost comparison calculation from the cost determination (e.g. Excel) via a defined CSV interface.

The dynamic cost comparison calculation (economic efficiency comparison) is prescribed for equivalent planning alternatives by the Federal Budget Code and, focused on water management, by DWA worksheet 100 and the guidelines of the State Water Workgroup (LAWA).

The dynamic cost comparison calculation can be used for the entire supply and disposal sector, for example for alternatives in sewer network, sewage works, water works or coastal protection planning. The following planning data are considered among others:

• Investment costs
• Ongoing costs
• Specific ongoing costs
• Reference parameters (such as wastewater volume) for the specific ongoing costs
• Cost development in the construction phase (up to 10 years)
• Up to three expansion stages for a facility
• Useful lives

A wizard guides you through the steps required for the dynamic cost comparison calculation. A maximum of four planning alternatives are imported via the CSV interface. Here the investment costs can be distributed over a construction phase of up to 10 years. A graphic (choice of logarithmic or linear) can be used to check the plausibility of the assessed costs.

The cash value of the cumulative cost is calculated by the dynamic cost comparison calculation per alternative for the chosen period under consideration (50 years for example). This value corresponds to the total costs to be incurred in the period under consideration that would have to be paid in cash on the reference date. The alternative with the lowest cash value of the cumulative cost should be implemented.

A sensitivity analysis of the input parameters (such as the real interest rate, real price increase, useful life) in coordination with the client may be decisive in favour of a different alternative.

The cost of the respective alternative, the development over time of the cash values of the cumulative cost and the results of the sensitivity analyses are calculated and shown graphically, and may be stored as an Excel or PDF file. DWA / LAWA requires an optimum rehabilitation strategy to permanently maintain sewer networks – determined using the dynamic cost comparison calculation between four time sequences of rehabilitation periods. The corresponding files can be imported into the economic efficiency comparison via the CSV interface (also from the network information system BaSYS). The preferred rehabilitation strategy is automatically determined from the four time sequences of the rehabilitation periods.