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Useful hints for the calculation of profitability

Default standard values

Default values are provided for the period under observation, the internal rate of return, price changes when replacing components, inflation, degradation of photovoltaic cells and the parameters for the automatic sensitivity analysis. These values are used for each new project or variant. These default values are partially based on norms and research results and have been set by Vela Solaris.

Savings are not income

Savings compared to a different variant (for example, heating oil saved because a heat pump is used) must not be considered as income from an economic point of view. These savings reduce costs and the savings effect is shown when different variants are compared.

How are new variants compared to the old, existing facility?

When comparing different new facility variants with an existing facility, the existing facility is modeled in Polysun and the values for its profitability determined. This way, the results of the profitability of the existing facility can be compared to the new solutions. This puts you in a position to point out for the long term what difference it makes if the old facility is left in place or is replaced by a new one. For this it is important that the full costs of each variant are considered and the same basic assumptions are used.

Dealing with electric consumers

The energy used by the electric consumers (for example, a private household) are treated like energy costs for purposes of profitability. If two variants are compared, you need to take care that both variants have identical electric consumers.

How is it defined whether electricity produced through PV will be fed into the grid or consumed?

In the features of the electric consumers, you can define under „With electric consumption of the thermal components“ (yes/no-answer) whether the electricity produced through PV will be used for the facility (pick „yes“) or will be fed into the grid (pick „no“).

What does the use of an electrical battery cost per energy unit?

If you install a PV plant, you are sometimes faced with the question whether the installation of a battery would be useful, for example to save the solar energy of the day for use during the night. The influence of a battery on profitability can be calculated comparing two otherwise equal variants, one with and one without battery. If all other parameters of the variants considered are equal (except for the presence or absence of a battery), the difference in energy production costs will reflect the costs for the battery per energy unit.

Video: Profitability calculation