Marstek VENUS D
A stackable AC-coupled balcony storage system with four solar inputs, 2.5 kW of bidirectional power and 2.5 kW of backup, built from 2.56 kWh battery modules.
- Best for solar plus backup
- AC battery
- 2.56 to 15.36 kWh
- 4 kW solar input
- Made by Marstek.
- Capacity: 2.56 kWh per battery module, with up to six modules for 15.36 kWh. The main unit itself holds no battery.
- Solar: four MPPT inputs for up to 4 kW of panels.
- Power: 2.5 kW bidirectional on-grid and 2.5 kW backup power, 3 kW for 10 seconds.
- Rules: whether you can use it as a plug-in battery depends on your country.
Not tested by us
We have not tested the Marstek VENUS D. The figures on this page come from the sources listed at the end of the page, checked on 11 November 2026, and we do not show prices. "Best for" is based on what the maker says the product is designed for, not on our own tests.
Key figures
15.36 kWh
Maximum with six battery modules
4 kW
Solar input, 4 MPPT
2.5 kW
Bidirectional and backup power
Specifications
Last checked on 11 November 2026. The grey text under each name explains what the value means.
| Specification | Value |
|---|---|
| Storage | |
| CapacityHow much energy the battery stores. Bigger means longer runtime or more of your own solar power used later. | 2.56 kWh per battery module (model MST-E2.5ST-D), 51.2 V. A system takes 0 to 6 modules, so 2.56 to 15.36 kWh in total. |
| Battery chemistryLFP (lithium iron phosphate) cells are known for long life and stable behaviour with heat. | Lithium iron phosphate (LiFePO₄) |
| Depth of dischargeHow much of the battery can be emptied without harming it. 90% means 10% is kept in reserve. | 90% |
| Cycle lifeHow many full charge and discharge cycles the cells are rated for before they hold less than the stated share of their original capacity. | Over 10,000 cycles at 80% capacity retention over 15 years or more on the product page. The Marstek datasheet lists more than 6,000 cycles at 25 °C. |
| ExpansionExtra battery units that add storage to the same system. | Up to six battery modules per system, for 15.36 kWh |
| Power | |
| AC output, grid-connectedThe lower output allowed when it feeds power into the home's circuits or the grid. | 0.8 kVA rated on-grid output (3.48 A at 230 V). The product page describes a 2.5 kW bidirectional inverter. |
| Backup outputA separate socket that keeps selected devices running when the grid is down. | 2.5 kVA rated, 3 kVA for 10 seconds, through a European socket (off-grid output) |
| Backup switchover (EPS)What happens when the grid fails. EPS means it takes over automatically. | Under 10 ms, according to the product page |
| AC charging inputHow fast it charges from a wall socket or the grid. | 2.5 kW bidirectional AC power (rated 2.5 kVA, 10.87 A at 230 V) |
| Efficiency and standby useLosses when charging, discharging and doing nothing. | More than 94.5% maximum battery-to-AC efficiency. Standby use is not stated. |
| Solar | |
| Solar inputsThe number of panel strings it can track separately (MPPT) and the total DC power. | Four MPPT inputs, up to 4 kW in total, 25 to 55 V, up to 32 A per input, MPPT efficiency 99.8% |
| Grid connectionThe supply type it is built for. Check it matches your home's supply. | AC-coupled, single phase (L/N/PE), 230 V, 50 Hz. Marstek says it works with existing solar systems and with Marstek, Shelly, HomeWizard and EverHome smart meters. |
| Connection and housing | |
| Dimensions (W × D × H)Check the space before you buy, including room around it for airflow and cables. | Main unit 480 × 320 × 105 mm and battery module 480 × 320 × 150 mm, as listed by Marstek (axis order not stated) |
| WeightMatters for lifting, wall mounting and moving it. | Main unit 17 kg, each battery module 24.6 kg |
| Protection ratingIP ratings show protection from dust and water. IP55 and IP65 are rated for outdoor-style exposure; check the installation guidance. | IP65 |
| Operating temperatureThe range it is rated to work in. Cold and heat can reduce performance. | -20 to 60 °C |
| Noise levelFan noise while working. | Under 30 dB |
| ConnectivityHow you monitor and control it, usually through an app. | Bluetooth, Wi-Fi, RS-485 and Ethernet; Marstek app, LED display and an open API |
| Warranty | |
| WarrantyThe period the maker covers. Read the terms: conditions and capacity guarantees differ. | 10 years |
Compatible with
What Marstek says this product works with. Anything not listed here is not confirmed.
- Smart meters
- Marstek lists Marstek, Shelly, HomeWizard and EverHome smart meters for anti-feed-in control.
- Existing solar systems
- Marstek says the AC coupling works with any existing solar system.
- Third-party energy management
- Marstek says an open API supports third-party energy management systems.
Rules where you live
Rules for plug-in batteries differ by country, and we could not confirm a version or plug for Great Britain. In Great Britain, plug-in solar kits of up to 800 VA have been legal since 27 August 2026, but the rules exclude plug-in batteries.
Check the rules, incentives and tariffs for your own country in our country guides.
Strengths and things to check
Strengths
- Four MPPT inputs for up to 4 kW of solar panels
- 2.5 kW bidirectional power and 2.5 kW backup
- Modular from 2.56 kWh to 15.36 kWh
- IP65 and under 30 dB
- 10-year warranty on the product page
Worth checking before you buy
- Whether it counts as a plug-in product depends on your country: check the rules below
- The main unit holds no battery, so you need at least one 2.56 kWh module
- Marstek's product page and datasheet give different cycle-life figures
- Marstek says final specifications and design will follow the commercial product
Change log
We record changes to this page here, so you can see when figures such as the warranty were last updated.
- 11 November 2026
- Page published. Warranty at publication: 10 years (Marstek product page). Marstek marks the VENUS D as new and says final specifications and design details will follow the commercially available product.
Where this information comes from
We have not tested the VENUS D. Every figure above comes from Marstek's VENUS D product page and its VENUS D datasheet (the EU presentation PDF on Marstek's download centre), last checked on 11 November 2026. The product page had no specification table, so size, weight and most electrical values come from the datasheet. A value these sources do not state is shown as not stated.
We do not show prices, because they change often and differ between sellers.
- Manufacturer Marstek VENUS D datasheet (EU presentation PDF, download centre)
- Manufacturer Marstek VENUS D product page
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Common questions about Marstek VENUS D
Can I use the Marstek VENUS D as a plug-in battery in my country?
It depends on local rules. In Great Britain, plug-in solar kits up to 800 VA are legal since 27 August 2026 but the rules exclude plug-in batteries. Check our country guides.
Does the VENUS D include a battery?
The main unit holds no battery. Marstek's datasheet lists it with 0 to 6 battery modules of 2.56 kWh each, so you add at least one module.
How much solar can the VENUS D take?
Marstek lists four MPPT inputs and up to 4 kW of solar input in total, at 25 to 55 V per input.
Related guides
How much could a battery save you?
Our calculator uses your own usage and tariff to estimate what a home battery could save, with conservative assumptions.