ᐅ Photovoltaic System: Costs and Savings Potential – Experiences?

Hello, a question for the group: As part of our building project, we are also looking into a photovoltaic system. It’s been difficult to find suppliers who are willing to provide a quote since construction has not started yet. We have now received a quote, but it seems a bit expensive to us. What do you think?

Total costs: approximately 31,500 EUR including VAT
- Photovoltaic system with 8.25 kW, about 13,500 EUR net
-> Heckert solar panels, 22 units each with 375 W capacity
-> complete installation including mounting structure (flat roof), inverter, etc. included
- Battery storage for about 13,000 EUR
-> option of Alpha Storno Smile5 with 11 kW or Senec Home with 10 kW

What is your opinion on Senec?

Not just somewhat expensive — very expensive.

With the battery storage, you usually only have the choice between somewhat unprofitable and extremely unprofitable, and in your case, it’s more the latter. But even the photovoltaic system itself is very overpriced at about 1650 EUR/kWp. For the total capacity, you should definitely aim for around 1100–1200 EUR/kWp.

I would like to revisit the topic of battery storage being unprofitable and virtual power plants (Stromcloud) being unprofitable, as I keep reading these claims here.

I have calculated for myself that both are worthwhile, and I would like to know if I am miscalculating or if I have forgotten something.

1. Virtual power plant (Stromcloud)

I currently pay €43.95 monthly to be able to withdraw 4,000 kWh of the electricity I feed into the grid during summer free of charge in winter. Any consumption beyond that is charged at €0.28 per kWh. I have transferred the feed-in tariff of €0.09 per kWh, which is paid directly by the grid operator to the virtual power plant operator. Any feed-in exceeding 4,000 kWh is paid out to me by the virtual power plant operator at the end of the year.

Current data for one year (October 1, 2020 – September 30, 2021):

Electricity drawn from the grid: 4,153 kWh
Electricity fed into the grid: 4,531 kWh

Costs:
12 * €43.95 = €527.40 fixed monthly fee
153 * €0.28 = €42.84 cost for excess consumption
531 * €0.09 = €47.79 refund for excess feed-in

€527.40 + €42.84 - €47.79 = €522.45 total cost

Comparison with a tariff without virtual power plant (data from provider comparison Verivox as of today):
Fixed fee: €15.40 monthly
Electricity cost: €0.28 per kWh

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

€184.80 + €1,162.84 - €407.79 = €939.85 total cost

Therefore, I saved €451.40 with the virtual power plant over one year.

2. Battery storage

We have a 10 kW battery. Cost: €6,000

In one year (October 1, 2020 – September 30, 2021), the battery stored and discharged 2,700 kWh.

If I had drawn this 2,700 kWh from the grid at €0.28 per kWh, it would have cost €756. Of course, I also have to consider that if I had not stored this electricity, I would have fed it into the grid and earned the feed-in tariff of €0.09 per kWh, which amounts to €243.

€756 – €243 = €513 savings

€6,000 / €513 = 11.69

So the battery would pay for itself in about 12 years.

What do you think? Have I calculated correctly? Did I forget or overlook anything?

Without going into detailed calculations, the tax aspect and storage losses are at least missing. "2700 kWh stored and then delivered" cannot be accurate, as charging and discharging cause about 15-20% loss.

More importantly, you are comparing apples to oranges—namely, a photovoltaic system with storage versus no photovoltaic system. This is incorrect because with the photovoltaic-storage option you have an initial investment, while in the second option you could invest that capital with interest over 20 years.

A proper comparison would be cloud service versus standalone photovoltaic with the same investment. Then it quickly becomes clear that the cloud provider’s profits and the uneconomical storage are cross-subsidized by the photovoltaic gains.

Furthermore, you would need to examine the contract. Can the provider raise purchase prices? By any amount? Can you exit after a certain number of years, or are you locked in? Who operates the system? What about VAT? What happens if the inverter or the storage unit fails?

Thank you for the quick response.

I left out the tax considerations because, for example, with the electricity cloud system it doesn’t make a difference whether it’s used or not. The tax burden is calculated based on self-consumption and feeding electricity into the grid, which is the same in both cases.
When it comes to whether to include a battery or not, there is naturally some difference, although I don’t expect this to significantly change the result. For 2,700 kWh either fed into the grid or self-consumed, the tax difference should be around €30 (about $33).

I can’t really follow the apples and oranges comparison. With the electricity cloud, I’m only comparing the situation with and without it. The photovoltaic system and battery are present in both cases.
For the battery, I’m only calculating the annual savings it provides and from when it becomes cost-effective. Of course, I didn’t factor in that the invested capital could be placed elsewhere for some return, that’s true.
And theoretically, the photovoltaic system without a battery would pay off faster than with one. But according to my calculations, the battery should also be worthwhile after a certain period, right? So far, I’ve only read that the battery never recovers its costs.

In short, if you really get the storage system at such a low price, and you don’t simply ignore the storage losses, you at least have a chance to break even after about 15 years.

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