Ü plant - Calculation of amortization

By way of introduction, we would like to deal with the term amortisation, or more precisely, the amortisation period. We will limit ourselves to the so-called static amortisation, which means that a system generates the same financial return year after year. The focus here is not on the energetic amortisation, i.e. the question of when the energy that was needed to manufacture and install the system was recovered.

The static payback calculation itself is very simple: the payback period is the time by which the initial investment has been earned back. Or mathematically: payback period=acquisition costs/annual return.

Figure 1: Analysis of the three calculation variants:

• Simulation photovoltaic system
• Simulation photovoltaic system + my-PV solution

Now an example of a Ü20 system in Germany. Because of the subsidy limit, this is twice as large, namely 10 kWp. After 20 years in operation, the investment has long since paid for itself through the special feed-in tariff. With the EEG 2021, however, the kWh fed into the grid will only be purchased at the market price of 4 cents. With a heat price of, for example, 8 ct/kWh, self-use, also for heat generation, is thus immediately interesting. But how long does it take for the additional investment in a my-PV solution to pay off?

Converting a full feed-in system into a self-consumption system costs about 700 €. This includes the conversion costs and a system check. Even the costs for the additional investment in my-PV are still manageable at €1,000.

With annual savings of about 233 euros, the system optimisation pays for itself in seven years. It can be expected that the photovoltaic system will be in operation for another 10 years after the end of the 20-year full feed-in period. This means that the system extension with my-PV is easily earned.

Figure 2: Simple calculation of the payback period of a Ü20 system in Germany (additional investment, conversion and payback).