Solarwatt Home Batteries: Battery flex and Manager

The Solarwatt Battery flex AC-1 is a modular, AC-coupled lithium-ion home battery offering 4.8 to 19.2 kWh of usable energy, built from two to eight battery modules connected in series¹. Because it is AC-coupled, it sits on the household's AC side rather than being wired into the solar panels' DC circuit, which means it can be fitted to an existing solar installation without replacing the inverter: Solarwatt states it is "suitable for existing and new installations"¹. The system is made in Germany, carries a 10-year warranty once registered, and is controlled through the Solarwatt Manager and the Solarwatt Home app¹.

For a household weighing energy independence, the Battery flex does the core job of a home battery: it stores electricity generated during the day for use in the evening, reducing what has to be bought from a supplier. What remains is the grid connection itself, the network operator's connection rules, and the manufacturer's cloud and app for monitoring and control. There is no published price for the Battery flex; as with most home batteries sold in the UK, prices are installer-quoted after a survey.

A modular AC-coupled battery from 4.8 to 19.2 kWh

The Battery flex AC-1 is what Solarwatt calls "a modularly expandable Lithium-ion battery storage system"¹. A complete system has three kinds of part: at least one Battery flex base AC-1 1.3, which is the electronics and control module with the built-in battery inverter; at least one Battery flex middle pack 1.3; and a Battery flex top pack 1.3 to close the stack³. The base unit handles the conversion between the battery's DC and the household's AC, while the packs are pure storage.

The capacity range runs from 4.8 kWh with two modules to 19.2 kWh with eight¹. That spread covers a modest home storing a day's generation through to a large household with a heat pump or an electric car to feed. The maximum rated real power is 6.0 kW², which sets how fast the battery can charge and discharge; more on what that means in practice is in battery power ratings. The chemistry is lithium-ion, certified to the "Safety guidelines for Li-ion household battery systems"², and the modules connect without any cabling, using a plug-in connection².

Battery flex base AC-1 1.3: the specifications

The base unit is the part that does the electrical work, and its figures are the ones an installer will check against your supply.

Two figures deserve attention. The 93.6% charge efficiency is the AC-to-battery figure only; the full round trip, out to the house and back, will be lower, and how that is worked out is explained in round-trip efficiency. The single-phase 230 V connection means the base unit suits a standard single-phase household supply; homes on a three-phase supply would need to discuss the arrangement with an installer. The IP54 rating allows some protection against dust and splashing water, and the 30 dB noise figure is quiet enough for a hallway cupboard, though siting and location rules still apply.

The datasheet also lists a FullCoverage insurance package with 5 years included and an optional 10 years¹, and the battery modules carry a cycle service life described as an "unlimited number of full cycles during the warranty period"¹.

Growing the system in 2.4 kWh steps

Each Battery flex middle or top pack 1.3 holds 2.4 kWh of usable energy¹, and Solarwatt states the system "can be extended in 2,4 kWh-steps"². A household can start with two modules at 4.8 kWh and add packs later as needs change, up to the eight-module ceiling of 19.2 kWh. The modules connect with a plug-in system "without any cabling"², which keeps an expansion visit short, though it is still electrical work that belongs with an installer.

The charging and discharging power scales with the number of modules. With two pack modules the base unit manages 1,900 W discharge and 1,700 W charge at maximum; with eight modules it reaches 6,000 W in both directions, with a nominal charging power of 4,800 W⁴. In practice that means a small two-module stack charges and discharges at a gentler pace, while a full eight-module stack can cover a kettle, a washing machine and more at once.

Installation is designed around the weight. Each battery module weighs 25 kg and the base unit 23 kg, which Solarwatt says makes "single person installation possible"¹. The packs are built for wall installation, with floor installation as an option⁵, and the housing is aluminium with an integrated battery fuse and 30 A current carrying capacity⁵. What a stepwise expansion means for a household's independence is worth reading alongside adding more batteries later and the general case for modular and stackable systems.

Warranty: 10 years, registration within three months

The headline is a 10-year product warranty², but the cover is conditional on registration. Solarwatt's warranty conditions require that "the Product has been registered at www.solarwatt.com within three months of the initial operation date"³. The datasheet likewise describes the warranty as "10 years after successful warranty activation"⁴. A buyer who misses the three-month window risks losing the long cover, so registration belongs at the top of the handover checklist.

The battery packs carry a 10-year performance warranty for "at least 80% of the usable energy content"⁵, meaning Solarwatt promises the modules will still hold 80% of their stated capacity at the end of the term, with an unlimited number of full cycles during the warranty period¹. How such retained-capacity promises are judged is covered in home battery warranties. If the home is sold, "this Warranty is transferred to the new owner of the Product to the extent of the remaining warranty period"³.

The exclusions are broad. Solarwatt's warranty does not cover damage from improper storage or transport, improper installation or removal, operation contrary to instructions, improper maintenance, improper modification or manipulation, force majeure, or manipulation or removal of the serial number or type plate⁶. Several of those turn on following the maker's instructions, which is one reason the installation process and the standards governing installation matter to the warranty as well as to safety.

The Solarwatt Manager and the Home app

The Battery flex is controlled through the Solarwatt Manager, which Solarwatt says "monitors, controls and regulates all energy flows in the house"⁷. The EnergyManager "measures, switches and visualizes all processes of the photovoltaic system and the appliances in the household", and it "creates both an output forecast for the PV-system and a demand forecast for the connected consumers"⁷. Consumers such as heat pumps or water heaters can be coupled, metered and controlled with additional devices, the EnergyMeter or Digital Extension⁷.

The Manager connects to two platforms: the SOLARWATT Manager portal, which runs in the cloud, and the SOLARWATT Home app⁸. Through the app a household gets real-time visualisation of generation, consumption, feed-in and electricity cost, personalised forecasts, manual control of storage and appliances, scheduling, and smart control optimised either for maximum solar self-consumption or for dynamic tariffs⁹. The Manager flex offers three switching modes: manual, time-optimised and PV-optimised¹⁰. Firmware and app updates arrive via an update server⁸, and the Battery flex itself is remotely updatable¹.

This is where the dependence sits. The battery stores energy whether or not the internet is working, but the forecasting, the tariff optimisation, the monitoring and the software updates all run through Solarwatt's cloud and app. A household that wants to keep control closer to home can compare the options in monitoring a home battery, and the tariff-optimised mode is only as valuable as the tariff behind it, a trade-off explored in batteries and smart tariffs.

Who Solarwatt is

Solarwatt GmbH is based at Maria-Reiche-Str. 2a, 01109 Dresden, Germany¹¹, and the company presents itself as a Dresden manufacturer: independent reporting describes it as "Dresden-based"¹² and records that "the final assembly of the SOLARWATT Battery flex energy storage system" took place at new Dresden production facilities opened as part of a 100 million euro investment¹³. The Battery flex datasheets carry the "quality Made in Germany" label¹. One Solarwatt datasheet from 2024 lists China as a place of production¹⁴, so the made-in-Germany claim is best read as applying to the Battery flex system rather than to everything the company sells.

The company's own scale figures are large: over 30 years of expertise, more than 13 million individual solar panels sold, more than 750,000 PV systems installed across Europe, 130,000 battery systems, heat pumps and EV chargers, and more than 1,000 craft installer partners⁹. Solarwatt began manufacturing solar modules in 1993⁹. For UK buyers, Solarwatt states it has "local offices and warehousing" giving "a strong UK presence"¹⁶, and general enquiries go to Solarwatt Technologies Ltd. at info.uk@solarwatt.com¹⁵, with warranty claims under the Battery vision conditions directed to support.uk@solarwatt.com¹⁷.

Certification and grid compliance: G98, G99 and G100

A home battery has to be told to the network operator, and the paperwork runs on standard UK grid codes. Solarwatt's UK-market documentation shows its inverters certified to EREC G98-1:2022, G99-1:2022 and G100:2022¹⁸, with the Inverter vision three 1.0 listed against G98-1:2022 Amendment 7, G99-1:2022 Amendment and G100:2022 Amendment 2¹⁸. The Battery vision datasheet also lists PAS 63100:2024 (UK) among its certifications¹⁸, the domestic battery installation standard covered in the standards governing home battery installation.

On the network side, the requirements are set by the operators, not the manufacturer. Northern Ireland's G99 fast track application asks for a "compliance certificate with test results"¹⁹, and Electricity North West explains that grid-code compliance is "an obligation under the Electricity, Safety, Quality and Continuity Regulations 2002"²⁰. In practice, the installer handles the G98 or G99 notification, and the maker's certificates are what make that notification possible. The process is set out in telling the network operator about a home battery.

How the Battery flex compares with other modular batteries

The Battery flex's distinguishing feature is its 2.4 kWh expansion step, one of the finest on the UK market. RCT Power's Battery Premium scales in 2.5 kWh steps²¹, and RCT's support documentation describes expansion "in 1.9 kWh steps up to max. 11.5 kWh"²². Jackery's SolarVault 3 expands up to 15.12 kWh with five BP 2500 expansion batteries²³. Against those, the Battery flex offers both a small step size and a high ceiling at 19.2 kWh.

On warranty, 10 years is the market norm rather than a differentiator: Which? notes that "battery systems often come with a 10-year warranty", and lists Tesla's Powerwall and SolaX systems at 10 years alongside the same figure for others²⁴. Solarwatt's 80% retained-capacity promise and unlimited full cycles during the warranty period¹ are terms worth comparing line by line, and the FullCoverage insurance with five years included¹ is an extra few makers match. The honest summary: the Battery flex competes on modularity, German assembly and the Manager's forecasting, while its warranty terms are standard for the class. What any battery actually delivers for self-sufficiency depends less on the badge than on sizing, tariff and use, the ground covered in home battery sizing and how much self-sufficiency a solar home battery can achieve.