Calculation of a photovoltaic system regarding economic efficiency

Hi everyone,

I tried just for fun to calculate the profitability of a photovoltaic system (once with, once without storage). Later, I'm also interested in how it behaves with increasing demand due to a heat pump. Of course, I had to make assumptions for this. I gathered the values to the best of my knowledge and belief from various sources:

[*]I assumed costs for photovoltaic and storage at 1600€/kWp and 1100€/kWp respectively (the latter is probably chosen too low)
[*]Yield: 1000 kWh per installed kWp per year.
[*]I assumed that I can only cover 30% of my own consumption with photovoltaic (70% with storage) because electricity is not always generated when it is needed or vice versa. So, electricity always has to be purchased even if the theoretically generated amount of electricity exceeds own consumption.
[*]Purchase cost 30 cents, feed-in tariff 9 cents

Based on these assumptions, I played around a bit and found:
It takes quite a long time for the investment to pay off. With my consumption (assumed 3500 kWh), not even after 12 years.
With storage, it actually never pays off (or only after about 25 years) because the acquisition costs are so high.

That seems a bit odd to me.
Here and in various other forums, I read that photovoltaic systems are actually always profitable nowadays, sometimes already after 7 years.
That's why I have little trust in my calculation.

Can someone maybe take a look at it?
Did I miscalculate? Or make massively wrong assumptions?

Thanks & best regards

For a house construction that you want to start within the next five years, you currently do not need an economic feasibility study for photovoltaics. At the moment, prices are rather crazy, and after the federal election, the cards will be reshuffled anyway (e.g., feed-in tariff, subsidies, etc.). Above all, I would also expect technological leaps and cost reductions in storage systems in the coming years.

If you really want to continue dealing with house designs, all you need to know about photovoltaics right now is to plan your house as photovoltaic-friendly as possible (well-oriented, as smooth roof surfaces as possible).

That the whole story is highly dynamic is clear. According to logic, one should never deal with any topic because everything changes again anyway. But what role does my other thread play if I perform calculations for the here and now out of pure interest? Ontopic: do you see any inconsistencies or false assumptions in my calculation anywhere?

Your air-to-water heat pump already consumes 3500 kWh, depending on the size of the house. We assume a sustainable consumption of 10,000 to 11,000 kWh. The system costs 33k including storage (18kWp and 12kWh). Amortization after about 10 years at full price. Net price set and 40% subsidy on the storage already about two years earlier. The technology never stands still. No matter when you buy, after two years everything is 'outdated'. Whether bought now or in five years.

I have not looked at the Excel. What do you want to "calculate" with exclusively unknowns? Especially into the - also unknown - future?

The gold rush days of photovoltaics are over and probably won't come back. Photovoltaics is still interesting if you optimize self-consumption (east/west orientation of the roof, heat pump, possibly storage). The funding landscape is constantly changing and I would currently assume in favor of renewable energies. Having photovoltaics on the radar and considering it in house planning is absolutely sensible from my point of view - you're already doing that correctly. The details will come later anyway ;)

We assume a sustainable consumption of 10,000 to 11,000 kWh with us.

Are you building the 220 sqm on the Zugspitze?:D Even including "household electricity" not up to date!