sonnen GmbH, based in Wildpoldsried in the Allgäu region and one of Germany's best-known makers of home batteries, filed for insolvency in self-administration on 22 October 2026. The company confirmed the filing about two months after Shell sold sonnen to the family office Tiven. Existing business and service are to continue for its more than 150,000 customers. According to sonnen, the filing covers sonnen GmbH only; electricity under the sonnenFlat is supplied by sonnen eServices GmbH, a separate company. For owners of a sonnenBatterie this means: the battery keeps working, the warranty remains a promise of sonnen GmbH, and your power supply continues in any case. What matters now is a battery that stays online, complete paperwork and a look at your own electricity contract.
As of 26 October 2026, 2:00 pm CET. Not legal advice, see the note at the end.
More on this topic: Battery Storage & Energy, with background, practice and every article in one place.
sonnen Insolvency: Key Facts at a Glance
- 22 October 2026: sonnen GmbH files for insolvency in self-administration; the existing management continues to run the company.
- More than 150,000 customers: existing business and service are to continue, according to Handelsblatt.
- Around 400 employees at the Wildpoldsried headquarters were informed on the morning of 22 October.
- 26 October 2026, midday: the German insolvency portal shows no official notice yet, so the court and the preliminary custodian are not public.
- 10 years or 10,000 cycles: the manufacturer's warranty on the sonnenBatterie 10, provided the battery stays permanently connected to the internet.
- Section 38 of the Energy Industry Act: if a supply contract ends, the local default supplier automatically keeps delivering power.
sonnen Insolvency: What Happened on 22 October
On the morning of 22 October 2026, the roughly 400 employees in Wildpoldsried learned of the insolvency filing, and the company confirmed it to Handelsblatt (pv magazine on the sonnen filing). A day later sonnen told the trade service Energie & Management that sonnen GmbH had applied for insolvency proceedings in self-administration. Customers and partners had been informed, and the filing applied to sonnen GmbH only (Energie & Management, 23 October 2026).
According to Handelsblatt, as summarised by the German utility trade paper ZfK, one production site is to remain. The subsidiaries in the United Kingdom and Italy are to be wound down, and the US business is to continue under a new company (ZfK on the sonnen filing). The same report carries the figures behind the filing: revenue fell from 443 million euros in 2023 to 198.9 million euros in 2024, and EBITDA for 2024 stood at minus 188.7 million euros. In 2025 a cost-cutting programme reduced the loss to 52.2 million euros.
sonnen was founded in 2010 and acquired by Shell in 2019, reportedly for almost 500 million euros. In August 2026 Shell sold the company to Tiven, the family office of Gert Purkert, co-founder of the investment firm Aurelius. According to Handelsblatt, Tiven planned to restructure sonnen and sell it on later (pv magazine on the sale to Tiven). How home batteries, grid-scale storage and the grid fit together is covered in my overview of battery and energy storage.
Self-Administration at sonnen: How the Insolvency Proceedings Work
In self-administration, the existing management keeps running the company under the supervision of a custodian (Sachwalter) instead of an insolvency administrator. This is set out in Section 270 of the German Insolvency Code. Until proceedings are opened, the court appoints a preliminary custodian if the company's plan is coherent (Section 270b). The procedure is designed to restructure a company rather than simply wind it down.
By midday on 26 October 2026 there was no official notice yet: the German insolvency portal showed no entry for sonnen since 12 October. Once the court has decided, the portal will list the court, the case number and the name of the preliminary custodian. If you search yourself, enter sonnen* with an asterisk in the company field; without it, the portal only looks for the exact name.
Two rules matter for customers. In self-administration, claims are filed with the custodian under Section 270f(2) of the Insolvency Code, and only once proceedings have been opened. After opening, the company itself decides on ongoing contracts, in agreement with the custodian (Section 279). Until then, contracts continue as they were agreed.
sonnenBatterie After the Insolvency: Battery, App and Warranty
The battery belongs to whoever bought it, and an insolvency filing does not change that. The sonnenBatterie keeps storing solar power and releasing it to the house in the evening. The app, the customer portal, software updates and participation in the virtual power plant, on the other hand, run on sonnen's systems. That is exactly why the commitment to continue service matters.
The manufacturer's warranty on the sonnenBatterie 10 runs for ten years or 10,000 cycles. sonnen pays out once capacity has fallen to 80 percent or below, and it requires the battery to be connected to the internet practically all the time. The Munich Regional Court upheld both clauses in 2019 after a lawsuit by the consumer centre of North Rhine-Westphalia (ZfK on the ruling on the sonnen warranty). That leads to the most important advice in this article: keep the battery online. If you disconnect it from the internet out of concern, you put the warranty at risk yourself.
The warranty is a promise made by sonnen GmbH. How warranty cases are handled during the proceedings is decided by the company together with the custodian. Statutory liability for defects is a separate matter: it lies with the business that sold and installed your battery, usually a local installer. Its obligations are unaffected by the sonnen insolvency.
sonnenFlat After the sonnen Insolvency: Who Supplies Your Power
The contracting party for electricity under the sonnenFlat is sonnen eServices GmbH, as stated in sonnen's FAQ on the sonnenFlat. It is registered at the Kempten commercial register under its own number and, according to sonnen, is not part of the insolvency filing.
Independently of the insolvency, the sonnenFlat is being phased out anyway. sonnen expects the tariff to end by the end of September 2026 and offers sonnenHome Energy with the EnergyFix and EnergyDynamic tariffs as its successor. There is no automatic switch; customers change in the sonnenApp or online (sonnen on switching to sonnenHome Energy). What applies to you is stated in sonnen's latest letter about your tariff.
The lights stay on in every scenario. If a supply contract ends, Section 38 of the German Energy Industry Act treats the power as delivered by the local default supplier, with no application and no interruption. This substitute supply ends as soon as you have a new contract, after three months at the latest, and the default supplier may charge its own prices for it. With a battery at home, a dynamic electricity tariff is worth a look, because the battery can make use of cheap hours.
sonnenCommunity, Virtual Power Plant and Feed-in After the sonnen Insolvency
The sonnenCommunity links customers' batteries. With the sonnenFlat you receive a free electricity allowance from the community; in return the battery becomes part of the sonnenVPP virtual power plant and helps stabilise the grid with small amounts of power, according to sonnen mainly through primary control reserve. These services depend on the platform of sonnen GmbH and therefore on the service that is to continue.
For feed-in, it depends on your contract. Under the sonnenFlat you assigned the solar power you feed into the grid to sonnen, which markets it. When the contract ends, the grid operator pays the statutory feed-in tariff directly again, at the same rate as before. Under the new tariff without direct marketing, the grid operator pays directly as well; with direct marketing through sonnen, revenues run through sonnen, and if they fall below the statutory value, the grid operator tops them up with the market premium. How far the fixed tariff for new systems is falling is covered in my article on the decline of the feed-in tariff.
If you later want to market your battery through another provider or charge it with grid power, you will meet the Federal Network Agency's rules that have applied since 21 October 2026. I explain them in my article on the MiSpeL rules for storage and charging points. And if you would rather share power with your neighbours than in a manufacturer's community, the legal framework is set out in my article on energy sharing in Germany.
Who Is Responsible for What at sonnen
Most questions resolve themselves once you separate who is responsible for which part. This overview helps you sort your own contracts.
| Area | Responsible | What applies now |
|---|---|---|
| Battery as a device | you as the owner | keeps working, stays online |
| Manufacturer's warranty | sonnen GmbH, in the filing | promise stands, meet the conditions |
| Liability for defects | installer who sold and fitted the battery | unchanged, first point of contact for faults |
| Power from sonnenFlat or sonnenHome Energy | sonnen eServices GmbH | not in the filing; without a contract the default supplier delivers |
| Feed-in payments | grid operator, or via sonnen under assignment or direct marketing | keep an eye on incoming payments |
| App, portal, community, virtual power plant | sonnen GmbH | continue with the service |
| Outstanding claims against sonnen GmbH | custodian | file only after proceedings are opened |
Checklist: What sonnen Customers Should Do Now
Seven steps are enough, and none of them costs money. If you take care of them today, you are prepared for any outcome of the proceedings.
- Keep the battery connected and online. The internet connection is a condition of the warranty and keeps the app, updates and virtual power plant running.
- Collect your documents: the installer's invoice, serial number, commissioning report, warranty terms, electricity contract and the assignment of your feed-in, as PDFs in one place.
- Save your figures: capacity, number of cycles and generation from the app or portal as a dated screenshot. These are exactly the values that count in a later warranty case.
- Check the letters about your tariff: is the sonnenFlat still running, have you switched to sonnenHome Energy, or does the latest letter give an end date?
- Check your feed-in payments: do they come from the grid operator or through sonnen, and did the last payment arrive on time?
- Report faults to your installer first and to sonnen's service in parallel, both in writing.
- Hold off on prepayments: pay for extensions and new components only once it is clear how the proceedings are going. You file claims with the custodian after proceedings have been opened.
Over the coming weeks, also expect letters from providers who want to use the situation. One example from this autumn: regarding letters from the company Deutsche Messwesen about installing smart meters, the consumer centre of Lower Saxony explains that recipients do not have to book an appointment; a smart meter becomes mandatory when the local metering operator announces it (consumer centre of Lower Saxony on the letters). When a smart meter is mandatory and when it pays off is covered in my article on the smart meter rollout 2026.
Senec, sonnen and the Home Battery Market: My Take
Two pioneers of the home battery have come under pressure within a single year. In July, EnBW ended the search for an investor for its subsidiary Senec and stopped taking new customers; service, statutory liability and warranties for existing customers continue there (pv magazine on Senec). Now sonnen follows. According to ZfK, Chinese suppliers such as BYD, Huawei and Sungrow now top the rankings.
My view as someone who works in the storage market: the technology is not the problem. Batteries in cellars and garages have delivered what they promise for years. What is under pressure is a business model in which the device, the electricity contract, the community and the virtual power plant all come from one source. That bundling made sonnen a pioneer, and today it makes customers dependent on the balance sheet of a single company. According to Handelsblatt, Shell invested more than another half a billion euros by 2025, and in 2025 there was still a loss of 52.2 million euros despite cost cuts.
Anyone buying a battery today should therefore be able to separate three things: the device, the electricity tariff and the marketing of its flexibility. A battery that works with different tariffs and marketers keeps its value whatever happens to the manufacturer. And that value is growing. With dynamic tariffs and the Federal Network Agency's new rules, a flexible battery at home is becoming worth more, not less. The idea behind the sonnenCommunity was right; it just needs to rest on more than one company.
Frequently Asked Questions
Is sonnen insolvent?
sonnen GmbH filed for insolvency in self-administration on 22 October 2026. As of 26 October the proceedings had not been opened and the insolvency portal showed no official notice. In self-administration, the existing management continues to run the company under the supervision of a custodian.
Will my sonnenBatterie keep working after the insolvency?
Yes. The battery belongs to you and keeps storing solar power. According to Handelsblatt, existing business and service are to continue. Keep the battery connected to the internet, because the app, updates, the virtual power plant and the warranty depend on it.
What happens to the warranty on my sonnenBatterie?
The manufacturer's warranty is a promise of sonnen GmbH and remains in place; for the sonnenBatterie 10 it covers ten years or 10,000 cycles until capacity falls to 80 percent, provided the battery is permanently online. How warranty cases are handled during the proceedings is decided by sonnen together with the custodian. The statutory liability of the installer who sold the battery is not affected.
Will I still get power through the sonnenFlat?
Power is supplied by sonnen eServices GmbH, which according to sonnen is not part of the insolvency filing. According to sonnen, the sonnenFlat is being phased out by the end of September 2026 anyway, with sonnenHome Energy as its successor. If a supply contract ends, Section 38 of the Energy Industry Act ensures that the local default supplier automatically supplies you.
Who pays my feed-in tariff?
In principle, the grid operator. Under the sonnenFlat your feed-in is assigned to sonnen; when the contract ends, the grid operator pays the statutory feed-in tariff directly again at the previous rate. Under sonnenHome Energy without direct marketing, it also pays you directly.
Where do I file claims against sonnen?
In self-administration, with the custodian, as set out in Section 270f(2) of the Insolvency Code, and only after proceedings have been opened. The custodian's name and address will then appear in the official notice on the German insolvency portal.
Note: This article is not legal advice. It reflects the situation on 26 October 2026, 2:00 pm CET. I will add the court, case number and custodian as soon as the official notice is published. For questions about your own contract, German consumer centres and lawyers specialising in insolvency law can help.
Best,
Dennis Weidner
Note: AI tools supported me in writing this article, and some images were edited with AI. I stand behind its content and every statement with my name.
