# Cost Assumptions¶

The database of cost assumptions is retrieved from the repository PyPSA/technology-data and then saved to resources/costs.csv. Cost assumptions of previous PyPSA-Eur versions can be restored by setting in the Snakefile: COSTS="data/costs.csv".

The config.yaml provides options to choose a reference year (costs: year:) and use a specific version of the repository costs: version:.

It includes cost assumptions for all included technologies for specific years from various sources, namely for

• discount rate,
• investment (CAPEX),
• fixed operation and maintenance (FOM),
• variable operation and maintenance (VOM),
• fuel costs,
• efficiency, and
• carbon-dioxide intensity.

The given overnight capital costs are annualised to net present costs with a discount rate of $$r$$ over the economic lifetime $$n$$ using the annuity factor

$a = \frac{1-(1+r)^{-n}}{r}.$

Based on the parameters above the marginal_cost and capital_cost of the system components are calculated.

## Modifying Cost Assumptions¶

Some cost assumptions (e.g. marginal cost and capital cost) can be directly overwritten in the config.yaml (cf. Section costs in Configuration).

To change cost assumptions in more detail, modify cost assumptions directly in resources/costs.csv as this is not yet supported through the config file.

You can also build multiple different cost databases. Make a renamed copy of resources/costs.csv (e.g. data/costs-optimistic.csv) and set the variable COSTS=data/costs-optimistic.csv in the Snakefile.