Photovoltaic system: Costs, saving potential? - Experiences?

Hello, a question to the group: As part of our construction project, we are also dealing with a photovoltaic system. It is difficult to find providers who will prepare an offer since we have not yet started construction. However, we now have an offer, which seems somewhat expensive to us; what do you think?

Total costs: approx. 31,500 EUR incl. VAT
- Photovoltaic system with 8.25 kW approx. 13,500 EUR net
-> Heckert solar modules, 22 pieces each with 375 W output
-> complete setup with mounting system (flat roof), inverter, etc. included
- Power storage with approx. 13,000 EUR
-> optionally Alpha Storno Smile5 with 11 kW or Senec Home with 10 kW

What do you think about Senec?

Not just somewhat expensive — very expensive.

For the storage, you only really have the choice between somewhat unprofitable and extremely unprofitable, with you leaning more towards the latter here. But the photovoltaic system itself is also very overpriced at about 1650 EUR/kWp. For the total capacity, you should definitely be aiming for around 1100-1200 EUR/kWp.

I would like to come back to the topic of storage=not profitable and Stromcloud=not profitable, since I keep reading this here. I have calculated for myself that both are worthwhile and would like to know if I am calculating incorrectly or have forgotten something or so.

1. Stromcloud

I currently pay €43.95 monthly to be able to draw 4,000 kWh of my electricity fed into the grid in summer back from the network free of charge in winter. Everything that is drawn beyond that is charged at 28 cents. I have assigned the feed-in tariff of 9 cents, which is paid directly by the network operator to the Stromcloud operator. The feed-in that exceeds 4,000 kWh is paid out to me by the Stromcloud operator at the end of the year.

Current data over one year (01.10.2020-30.09.2021):

Drawn from the grid: 4,153 kWh
Fed into the grid: 4,531 kWh

Costs:
12 * 43.95 = €527.40 basic fee
153 * 0.28 = €42.84 cost for additional consumption
531 * 0.09 = €47.79 repayment for excess feed-in

€527.40 + €42.84 - €47.79 = €522.45

Comparison with tariff without Stromcloud (data from provider comparison Verivox as of today)
Basic fee: €15.40 monthly
Purchase price: 28 cents per kWh

Costs:
12 * 15.40 = €184.80 basic fee
4,153 * 0.28 = €1,162.84 cost for grid consumption
4,531 * 0.09 = €407.79 feed-in tariff repayment

€184.40 + €1,162.84 - €407.79 = €973.47

I have therefore saved €451.02 in one year through Stromcloud.

2. Storage

We have a storage unit with 10 kW. Cost: €6,000

The storage unit stored and delivered again 2,700 kWh in the period of one year (01.10.2020-30.09.2021).

If I had drawn these 2,700 kWh from the grid, I would have paid €756 at 28 cents/kWh.
Of course, I also have to offset that if I had not stored the electricity, I would have fed it in, which gives a feed-in tariff of €243.

€756 - €243 = €513 savings

6,000 / 513 = 11.69
After almost 12 years, the storage unit would have paid off.

What do you think about this? Have I calculated correctly? Forgotten or not considered anything?

Without doing the calculations in depth now, at least the tax considerations and storage losses are missing. "2700kWh stored and released again" cannot be true, since about 15-20% loss occurs during charging and discharging.

Above all, you are comparing apples and oranges, namely a photovoltaic system with storage against no photovoltaic system. This is wrong, because with the photovoltaic-storage variant you have an initial investment, whereas with the second variant you could also invest this capital with interest over 20 years.

The correct comparison would therefore be cloud versus pure photovoltaic with the same investment. And then it quickly becomes clear that the profits of the cloud provider and the uneconomic storage are cross-financed by the photovoltaic profits.

Furthermore, one would have to look at how the contract is structured. Can the provider increase the purchase prices? To any extent? Can you opt out after x years or are you at their mercy? Who operates the system? What about the value-added tax? What happens in case of a defect in an inverter or the storage?

Thank you very much for the quick response.

I left out the tax considerations because, for example, with the Stromcloud it makes no difference whether it is with or without. The tax burden is calculated based on self-consumption and feed-in, and this is the same for both options.
When it comes to the question of with or without storage, it does of course make a certain difference, although I do not assume that the result would be pushed strongly in a different direction because of that. For 2,700 kWh either fed in or consumed yourself, the tax difference should be about €30.

Unfortunately, I cannot understand the apples and oranges comparison.
With the Stromcloud, I am only comparing how it is with and without Stromcloud. Photovoltaic system and storage are present in both cases.
When it comes to the storage, I am only calculating the savings per year from the storage and from when it becomes profitable.
That I could of course also invest the capital used for a certain return, I have not factored in, that is correct.
And theoretically, the photovoltaic system would amortize faster without storage than with storage. But according to my calculations, the storage should also pay off after a certain period, shouldn't it? Because so far I only keep reading that the storage cannot recoup its costs.

Short and concise, if you really get the storage that cheap, you at least have the chance to break even after ~ 15 years, if you don't simply ignore the storage losses.

Does anyone actually know of a storage that has lasted that long before?