ᐅ Experiences with Caterva Solar Battery Storage Systems

Hello everyone,

I am currently planning to install a Caterva Solar system (21 kW battery storage) for my new single-family house, which also provides grid balancing services through Caterva.

Unfortunately, I couldn’t find any results using the search function, so I would like to know if anyone here has experience with this or has received advice on it?

Thank you very much for your feedback.

Hello Dennis,

I don’t have experience with this system, but what would you like to know?

It’s unlikely to be economical, and I don’t really understand why you would need a 20 kW storage, especially since you would first need a photovoltaic system to charge it during winter.

Dennis86 schrieb:
To me, it sounds interesting at first that you can use the electricity generated on your roof throughout the year over a 20-year period, and only the demand beyond that needs to be drawn from the grid.

But that is purely sentimental thinking. With your existing air-to-water heat pump, you have a major consumer whose operating hours you can, for example, schedule with a timer for midday. Just by doing this, you will be able to use 40-50% of your photovoltaic electricity yourself. Battery storage is not worthwhile; it is very expensive and the durability is poorly guaranteed. Not cost-effective. This applies especially to the one you chose, as it is massively oversized. For your 8.5 kWp (kilowatt peak) photovoltaic system (which is actually a poor sizing choice, better to have around 7 or 10), a 5-6 kW battery is more suitable. In winter, when you need a lot of electricity for heating, photovoltaic output is low anyway, so all the electricity goes directly to the air-to-water heat pump and house consumption, and the battery just sits empty.

Dennis86 schrieb:
From my understanding, this goes well beyond a normal battery storage.

Yes, it involves a fairly complex business model that requires you to make a large upfront investment in unnecessary capacity with the promise of recovering it over decades. I wouldn’t throw my money at a startup like that, and I imagine your bank will insist that the battery is a personal expense (not eligible for financing through a mortgage). But you’ll have to clarify that yourself.

Dennis86 schrieb:
Honestly, I don’t have much confidence in current 6-7 kW batteries because you are still dependent on the electricity market (self-sufficiency rate about 70-80%) and it does not solve the problem of the mismatch between electricity generation (summer/day) and electricity demand (winter/night).

As I said, this is not about financial returns but sentimentality. That’s perfectly fine. Just don’t expect to be financially better off with it. That is completely unrealistic.

Dennis86 schrieb:
My problem is: I’m looking for the catch!

The calculation. For €27,000, you can buy electricity for a very long time. You can already achieve a considerable degree of self-sufficiency with photovoltaic and heat pump. Everything you add on top of that is completely uneconomical.

Looking for the catch? That was a good one.

Where exactly is the electricity supposed to come from when your battery is empty? Do you think the sun in Flensburg will shine like in midsummer on December 21st while your battery in Passau is empty and your photovoltaic system isn’t producing any power?

I believe that from an ecological point of view, this can be a great idea. However, economically it is definitely not reasonable, since the cost per kWh will probably be significantly higher than what would be economically viable.

Why do you need 20kWh in your battery?

Thank you for your feedback.

For me, these are the main reasons in favor of purchasing:

- A guaranteed community bonus of 1000 EUR per year (paid monthly). Of course, I am aware that Caterva is a limited liability company and could potentially cease to exist at any time. However, I don’t believe this will happen. As a Siemens subsidiary that has invested significant money and resources to obtain approval from the Federal Network Agency, it follows a viable business model.

- An electricity credit equal to the annual output of the photovoltaic system (about 1000 kWh per kWp with south-facing orientation in my region, according to various solar installers and photovoltaic owners), regardless of the fact that I need a lot of electricity in winter but generate it mostly in summer. Of course, in winter everyone’s storage is “empty,” but this is compensated accordingly by Caterva. Effectively, I only draw from the grid what exceeds my annual production.

All of this is contractually secured for 20 years. Any repairs and maintenance of the storage system are commissioned and paid for by Caterva, as required by the Federal Network Agency and a condition for granting the regulation services license.

I think you have to first understand the business model rather than just seeing it as a 20 kW storage system. For me, it’s clear: either this one or none.

Hello Toxicmolotov,

The concept at Caterva is completely different from other “regular” storage systems. The state of charge doesn’t matter at all—whether it’s summer, winter, day, or night. What really counts is the annual energy production. You can use that energy whenever you want, up to 10,000 kWh (10,000 kWh) per year for 20 years.