The Sigenergy SigenStor is a modular home battery system that combines a solar inverter, a battery inverter and energy management in one stacked unit, with up to six battery modules giving a maximum of 52.56 kWh of usable storage per stack. Its biggest strength is flexibility, because you can mix module sizes and add storage years after installation. Its biggest catch is that the inverter rating is fixed, so the one decision you can't easily change later is the one to get right first.
What is the Sigenergy SigenStor?
SigenStor is made by Sigenergy, a company founded in 2022 in Shanghai by former engineers from Huawei's FusionSolar division. It has become one of the most popular home battery systems in the UK.
The system has three main parts. On top sits the Energy Controller, which acts as the brain: solar inverter, battery inverter and energy management in one box. Below it, the battery modules stack up. Two optional extras complete the range: a DC electric vehicle charger and the Sigen Gateway for power cut backup.
Choosing the right inverter size
The single-phase Energy Controller comes in sizes from 3 kW to 12 kW. That range means you can match the inverter to your roof and your DNO connection rather than being forced into one fixed unit.
Size also decides how many solar inputs (MPPTs) you get. Models up to 6 kW have two, the 8 kW has three, and the 10 kW and 12 kW have four. Each MPPT runs a separate string of panels independently, so on a roof with panels facing several directions, or shade on one side only, each section performs to its own potential. On a complicated roof, that can remove the need for optimisers or microinverters.
Each controller accepts up to twice its rating in solar panels. A 12 kW controller can take up to 24 kW of panels, which is over 50 panels.
The inverter rating is fixed
Some systems, such as the Tesla Powerwall 3, let the inverter rating be adjusted in software. SigenStor doesn't. If you install an 8 kW controller and later want a bigger system, you need a new controller, which is expensive.
So think about where your home is heading over the next decade (an EV, a heat pump, more panels) before choosing. Remember that anything above 3.68 kW per phase needs DNO approval before installation, so the inverter size you want also has to be one the grid will accept.
How much a SigenStor battery actually stores
Sigenergy currently sells two battery module sizes, the BAT 6.0 and the BAT 10.0. The names aren't the usable capacities. The BAT 6.0 gives 5.84 kWh of usable storage and the BAT 10.0 gives 8.76 kWh, roughly 87% of what the label suggests. When comparing batteries, always compare usable capacity, not the name on the box.
You can mix module sizes in the same stack and add more later. Six BAT 10.0 modules on one stack give 52.56 kWh of usable storage.
Sigenergy has committed to keeping the modules the same physical size as cell technology improves. When SigenStor first launched in the UK the modules were smaller, and the current ones drop into those earlier stacks. That means any batteries you add later can be the newest version, not the same model you started with.
How many batteries should you start with?
For the best financial return, start slightly undersized. A battery earns its keep by cycling fully, ideally charging and discharging once a day. An oversized battery never empties, so part of what you paid for sits idle and the return drops.
The sensible approach is to install a little less storage than you think you need, live with it for a year, then look at the data. If more storage would pay for itself, add a module. SigenStor's modular design is built for exactly that.
Charge rate: the inverter sets the ceiling
Each BAT 6.0 module charges and discharges at up to 3 kW, and each BAT 10.0 at up to 4.6 kW. Add modules and those rates add up, but the system always runs at whichever is lower: the batteries' combined rate or the inverter rating.
Two BAT 10.0 modules could deliver 9.2 kW between them. Paired with a 6 kW controller, you get 6 kW. That matters most on larger systems.
Does the SigenStor give power cut protection?
Not as standard. Backup needs the Sigen Gateway, which sits between your incoming supply and your consumer unit. If the grid goes down, it disconnects the house and runs it from the battery and solar. The changeover is fast enough that your lights shouldn't flicker.
On a single-phase supply, the Gateway can run up to three SigenStor stacks and back up a full 100 amp supply. Three-phase Gateways go up to industrial scale. There is also a smart port for controlling specific loads, and a generator input for topping up the batteries in an extended outage.
The DC EV charger: who it suits
Sigenergy's DC EV charger slots into the stack in place of one battery module, so you can have six batteries, or five batteries plus the charger. It comes in 12.5 kW and 25 kW versions and uses CCS2 connectors only, so check your car's charging port first.
On a single-phase supply the inverter tops out at around 12 kW. The 25 kW charger could only draw about 12 kW from the grid, with the rest coming from the battery or solar, which needs a very large battery to be useful. For most single-phase homes, the 12.5 kW model is the better fit.
The charger is bidirectional, so the hardware could send power from the car back to the house. Vehicle-to-home and vehicle-to-grid aren't commercially available in the UK yet, but the capability is there if that changes.
Can the SigenStor be installed outside?
Yes. The system is IP66 rated. Cold weather is the bigger issue. Batteries lose efficiency below about 5°C, and the charge rate drops significantly. Each SigenStor module has a built-in heater that keeps the cells at around 10 to 15°C, and the system checks the weather forecast so it can warm up before a cold snap. It will cope with a British winter outdoors.
It can't actively cool itself, unlike the Tesla Powerwall 3. In a hot summer, expect it to run a little less efficiently.
Wall mounting is possible, but only for the controller plus a maximum of two battery modules. Anything larger goes on the floor. If you might expand beyond two batteries, floor-mount from the start.
Is SigenStor’s AI mode worth switching on?
The SigenStor app shows solar generation, battery level, grid use and household consumption on its home screen, with each battery stack visible individually. You enter your import and export tariffs, and the system works out how to run the battery. It also works with dynamic tariffs such as Octopus Agile, where prices change through the day.
There are two operating modes. Standard mode uses a fixed algorithm based on your solar, consumption and tariff. AI mode takes full control until you switch it off, learning how your household actually uses electricity and matching that against changing prices.
Sigenergy's own UK case study found AI mode saved around 20 to 25% more than its standard mode. That figure compares Sigenergy against itself. There's no published comparison with Tesla's or Fox's optimisation software.
SigenStor warranty
The battery modules and Energy Controller carry a 10-year warranty, extendable to 15 years with a paid extension. The Gateway is covered for 5 years, extendable to 10. The DC EV charger has a 3-year warranty.
How much does a SigenStor cost?
Every system is designed around the home, so prices vary. As a guide, a SigenStor with a 12 kW Energy Controller, two BAT 10.0 modules (17.52 kWh usable) and the Gateway for backup costs around £9,300 fully installed. A fully loaded stack of six BAT 10.0 modules (52.56 kWh usable) is closer to £20,000. The DC EV charger adds roughly £1,500 to £3,000 depending on the model.
Timing affects the price too. Battery storage installed in UK homes is currently zero-rated for VAT until 31 March 2027. From 1 April 2027 it is set to move to the 5% reduced rate unless the government extends the relief, and no extension has been announced so far.
Spirit Energy installs SigenStor alongside the Tesla Powerwall 3 and Fox EVO, and sizes each system from the household's actual electricity usage rather than a standard package.
