Consultation for photovoltaic systems

It depends on the roof pitch. I have read that up to 25° north can also make sense. But the efficiency decreases significantly. I had it calculated for my location using PVGIS and while I get 1000 sun hours for my SE and SW surfaces at 25° roof pitch, the two north-facing surfaces only get 7xx sun hours. So about 25-30% loss.

Exactly this calculation using PVGIS should also be done by the thread starter for his conditions. The yield on northeast will be lower. But you also have to remember that the additional modules installed on the NE side cost significantly less per kWp, since the installation costs are spread over many more modules. So you have to compare the total yield and costs for SW and SW+NE. Especially now, when the feed-in tariff falls into the range of production costs, self-consumption brings good savings. In diffuse light due to clouds, the increased module area also helps cover self-consumption better. I would definitely calculate it and if it makes even approximate sense, go for it.

I don't actually know the exact roof pitch :D but it will be 30-35 degrees and thus probably uninteresting again.

I will ask about the roof pitch at the next opportunity.

What do you think about a photovoltaic terrace roof?

With the orientation, the pitch of the NE side can actually be good. Don't guess, calculate it concretely!

Photovoltaic terrace roofs are nice. However, as far as I know, you need glass-glass modules there. These are significantly more expensive than glass-film modules, which are normally used on roofs. But as a hobby and with good orientation, definitely worth considering.

Storage becomes economically viable from about €250 per kW.

Definitely not with this information!

how can I calculate the photovoltaic system myself to determine what makes sense?

how can I calculate the photovoltaic system myself to see what makes sense?

Roughly as follows:

First, you can calculate the yields of both roof halves with PVGIS in kWh/year.
Depending on your expected energy consumption (heat pump, server farm, swimming pool?), you can cover a good part of your electricity consumption with photovoltaics. You do not get feed-in tariffs for this, but you save the costs of purchasing electricity from your energy supplier. In our household without major individual consumers, we can cover about 50% of self-consumption just by running the dishwasher and washing machine during sunny periods. An electric car, which is sometimes at home during the day and charged, increases self-consumption even more.
For the rest, you receive a feed-in tariff currently around €0.07/kWh. You get this for the year the system is commissioned plus another 20 years.

That gives you your annual income.

Then you determine the costs. This is mainly the depreciation of the system at 5% of the system cost per year over 20 years. In addition, there are ongoing costs for insurance (max around €100 per year), possibly maintenance and cleaning (typically near zero), replacement of an inverter (approx. €1500) typically after 10 years.

With income and expenses, you can calculate your profit/loss. You will notice that a major factor for profitability is a cheap purchase of the system.

Solar installers also make such calculations for you as part of their offers. However, they typically calculate with high annual increases in the electricity price. This can be used to make the costs of a storage system look better unnoticeably. The storage system increases your self-consumption slightly. However, you will never be able to cover 100% of your own demand. Therefore, a storage system is usually still too expensive and unprofitable in most cases.

With the calculator from Stiftung Warentest you can also play around a bit with the parameters, I find it quite good for that. Just be careful with the point where self-consumption is asked. This does not mean how much of your electricity consumption you cover percentage-wise with photovoltaics, but how much of your total photovoltaic electricity yield you consume yourself.