From ESS News

Hamburg-based digital utility Rabot Energy launched its new standalone home battery designed specifically for apartment renters in June 2026, and ESS News had the chance to speak with Konrad Schade, chief operating officer and managing director at the company, about both the launch and the concept driving the sale of a third-party battery, at IFA 2026.

Rabot Energy is one of the newcomers to retail electricity in Germany, being far more app-based and friendly than traditional retailers. The competition in this space is new and relatively exciting, with the likes of Octopus Energy and Ostrom playing in a similar markets, often with sign-up bonuses offered.

To work on customer loyalty over longer periods, Rabot Energy is offering a home battery that you can plug-in without requiring any electricians, or even a smart meter. Rabot Energy sells it at cost, and offers further discounts, while believing it can pay itself back rapidly thanks to dynamic tariffs.

Branded as the Rabot Flow, the 2.12 kWh plug-and-play battery is a standalone module. It charges directly from the grid during low-price hours and discharges when dynamic prices spike, and the system doesn’t offer integration with balcony or plug-in solar systems. That, said Schade, wasan intentional economic choice rather than a hardware flaw.

“Combining solar and grid charging in small balcony systems creates complex renewable accounting issues under German EEG law, requiring additional meters that ruin the economics for small tenants,” Schade explains. Standalone grid charging achieves virtually identical benefits.

“In 2023, Germany experienced roughly 1,000 hours of negative or zero electricity prices,” Schade says, noting that on days like May 1st, prices dropped to -€0.40 (-0.46)/kWh, effectively paying dynamic tariff users to charge their devices.

In essence, solar generation during that time is only useful if it’s charging a battery. But if you can get paid to charge your battery, the economics might stack up without solar on the balcony.

Background

Historically, Germany’s residential energy transition has been via homeowners investing in rooftop PV and battery storage. This has left the country’s millions of apartment renters locked into rigid, expensive fixed-rate contracts.

“We started Rabot Energy because the German energy market has been outdated for decades,” says Konrad Schade. “While the generation side has transformed with volatile renewables, customers have remained on fixed-price tariffs. The solar boom has only benefited the roughly eight million households with their own roofs. Normal apartment tenants have been completely left out.”

To bridge this “solar gap,” Rabot Energy teamed up with battery manufacturer Marstek to offer the Marstek Venus A as the Rabot Flow solution. Retailing at €400, the indoor lithium-iron-phosphate (LFP) device plugs directly into standard household wall sockets.

Schade said that it would soon switch to the Venus E Mini, which Marstek introduced at Intersolar 2026, and rebrand it. It remains a 2 kWh module, but this time it is entirely AC-only, without direct solar panel input. It weighs 22kg, just light enough to be portable and move when renters move.

This simple installation is thanks to a range of regulatory updates over past years, which relaxed German standards to allow small-scale residential storage under 800 W to be installed without a certified electrician. Additionally, recent rules protect standalone batteries from being charged double grid fees when storing power, establishing that energy drawn from the grid, stored, and fed back is legally classified as “stored grid energy”.

However, that 800 W cap introduces a technical limitation for arbitrage. “Because price spikes in spot markets often last only 30 minutes, a larger battery capped at 800 W output cannot discharge fast enough to capture the full price peak,” Schade notes. Consequently, running multiple smaller 800 W units across different socket circuits is actually smarter than using one large battery.

Making this billing work in Germany’s highly fragmented grid is an administrative hurdle. The country is split among roughly 800 distribution system operators (DSOs).

“We have had to talk to almost all of them to explain the legal framework,” Schade notes. “Even though the law is clear, 95% of DSOs don’t have automated systems to handle corrected grid-fee billing.” Rabot started testing manual invoice corrections back in February, with the initial payback iteration taking four months to complete.

Avoiding smart meters

While 15-minute spot market arbitrage technically requires a smart meter, Rabot Energy enables consumers without one, or those caught in Germany’s typical eight-week metering installation backlog, to deploy the Rabot Flow immediately under standard load profile (SLP) tariffs.

By simply connecting the plug-and-play battery to the Rabot Energy app, users unlock a guaranteed flat-rate saving of €120 per year credited directly to their account.

This fixed-payout model effectively bypasses Germany’s rollout bottlenecks, allowing apartment tenants to begin monetizing grid flexibility, while their digital meter installation is processed in the background.

API limitations

Interestingly, only Marstek would play ball with Rabot Energy’s needs.

“We talked to everyone, EcoFlow, Anker, you name it,” Schade tells ESS News.

“Marstek was the only manufacturer willing to build a dedicated cloud API connection for us to steer the storage remotely. The others weren’t interested. Without an open API, we would have had to attach physical control hardware to the smart meter down in the basement. In apartment buildings, tenants’ meters are in shared basements, making physical wiring impossible.”

“We pass the battery through one-to-one at cost without taking a profit margin,” he adds. “And, I’m meeting with Marstek in September to block larger hardware quantities, aiming to bring wholesale costs down, and we can rebrand them potentially.”

Loyalty

Rabot Energy is selling the Rabot Flow hardware at cost, and it offers a month-to-month contract versus a lock-in term. The complete flexibility is an advantage for retention, though.

“We pass the hardware cost directly through because the real value for us is customer retention,” Schade explains. “Even though our dynamic tariff can be cancelled monthly, and the battery is not locked to our system, over 90% of buyers connect the battery to our app and stay with us long term. It’s a win-win-win: the customer saves money, we eliminate churn, and decentralized batteries help stabilize the power grid.”

In Germany’s competitive energy market, customers frequently switch providers to chase sign-up bonuses. By integrating the battery with Rabot Energy’s dynamic tariff via a direct API connection to Marstek, the system automatically schedules charging during near-zero or negative price windows. This yields an estimated €120 or even €130 in automated annual savings for the customer.

With around 180,000 customers currently across Germany, Rabot Energy is now planning to expand into Austria and Poland next.