Marstek SATURN B2500-D
A balcony battery with two solar inputs and 2.24 kWh of storage that sits between your panels and a micro-inverter, adding up to 800 W of DC output.
- Best for micro-inverter setups
- Plug-in battery
- 2.24 kWh
- 1,600 W solar input
- Made by Marstek.
- Capacity: 2.24 kWh (2,240 Wh) with LiFePO4 cells. Several units can be linked: four units with one 800 W micro-inverter reach 8.96 kWh and 4,800 W of solar input, says Marstek.
- Solar: two MPPT inputs, up to 800 W each, 12 to 59 V.
- Output: two DC outputs of up to 400 W each (800 W in total) into a micro-inverter. It has no AC output of its own.
- 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 SATURN B2500-D. The figures on this page come from the sources listed at the end of the page, checked on 13 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
2.24 kWh
Capacity
1,600 W
Solar input, 2 MPPT
800 W
DC output to a micro-inverter
Specifications
Last checked on 13 November 2026. The grey text under each name explains what the value means. To see it next to other products, compare it in our comparison tool.
| Specification | Value |
|---|---|
| Storage | |
| CapacityHow much energy the battery stores. Bigger means longer runtime or more of your own solar power used later. | 2,240 Wh (2.24 kWh) |
| 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. | Adjustable in the app. Marstek suggests 50% in winter and 30% in very cold weather. The maximum is not stated. |
| 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. | More than 6,000 cycles to 80% capacity |
| ExpansionExtra battery units that add storage to the same system. | Several units can be connected. With a 2 MPPT 800 W micro-inverter, Marstek says up to four units give 8.96 kWh and 4,800 W of solar input. |
| Power | |
| AC output, grid-connectedThe lower output allowed when it feeds power into the home's circuits or the grid. | No AC output. The two MC4 outputs deliver up to 400 W each (800 W in total, 16 to 40 V, 15 A maximum) to a micro-inverter, which feeds the grid. |
| AC charging inputHow fast it charges from a wall socket or the grid. | No AC charging input is listed. Surplus solar power is stored. |
| Efficiency and standby useLosses when charging, discharging and doing nothing. | Not stated |
| Solar | |
| Solar inputHow much solar panel power it accepts. A higher figure fills the battery faster on a sunny day. | Two MC4 inputs, up to 800 W each, 12 to 59 V, up to 13.5 A each. Marstek says the device has two input specifications, 1,000 W and 1,600 W, and the rated voltage is 59 V. |
| Grid connectionThe supply type it is built for. Check it matches your home's supply. | Not connected directly: it works between the panels and a micro-inverter. Marstek says it works with its smart meter in Auto mode (real-time output to cover household load) or in Manual mode (fixed output during set periods), and with almost all micro-inverters that use MC4 connectors. |
| Solar and off-grid | |
| Works with solar panelsWhether you can charge it from solar panels. Yes means a built-in solar input or a compatible solar setup; read the detail for the voltage and power limits. | Yes: two MC4 inputs, up to 800 W each (1,600 W in total), 12 to 59 V. |
| Off-grid useWhether the maker describes it running with no grid connection at all, for example in a cabin, van or off-grid home. Backup only means it covers power cuts but needs the grid the rest of the time. | No: Marstek describes a balcony system that feeds a micro-inverter and has no stand-alone AC output. |
| Connection and housing | |
| Dimensions (W × D × H)Check the space before you buy, including room around it for airflow and cables. | 309 × 175 × 350 mm, as listed by Marstek (axis order not stated) |
| WeightMatters for lifting, wall mounting and moving it. | 20 ± 0.5 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. | -10 to 50 °C (storage -10 to 55 °C) |
| ConnectivityHow you monitor and control it, usually through an app. | Bluetooth 5.2 and 2.4 GHz Wi-Fi; Marstek app. Marstek says it does not offer MQTT access to individual customers. |
| CertificationsSafety and grid standards the maker says the product meets. | EN IEC 62109-1 and -2, EN IEC 61000-6-1 and -3, IEC 62619:2022, WEEE, RoHS, REACH |
| 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.
- Micro-inverters
- Marstek says it works with 99% of micro-inverters through MC4 connectors. For two MPPT inputs it names a 2 MPPT 800 W micro-inverter as the example.
- Marstek smart meter
- Marstek says its smart meter sends household consumption data to the battery, which adjusts its output in real time.
Rules where you live
Rules for plug-in batteries differ by country. This unit works as DC storage ahead of a micro-inverter, so the rules for the micro-inverter and the solar kit matter too. 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, and we could not confirm how this product fits.
Check the rules, incentives and tariffs for your own country in our country guides.
Strengths and things to check
Strengths
- Two solar inputs for up to 1,600 W of panels
- Works with almost all micro-inverters through MC4 connectors
- IP65, with more than 6,000 cycles and a 10-year warranty
- Several units can be linked for up to 8.96 kWh
Worth checking before you buy
- It needs a separate micro-inverter, because it has no AC output of its own
- Capacity is 2.24 kWh per unit, much less than the AC-coupled VENUS models
- Whether it counts as a plug-in product depends on your country: check the rules below
- Marstek gives the dimensions without stating which number is width, depth or height
Change log
We record changes to this page here, so you can see when figures such as the warranty were last updated.
- 13 November 2026
- Page published. Warranty at publication: 10 years (Marstek product page and FAQ). Marstek's product page calls it the SATURN-C B2500 in places and the B2500-D in others.
Where this information comes from
We have not tested the SATURN B2500-D. Every figure above comes from Marstek's product page for the B2500 balcony energy storage system, including its specification table and FAQ, last checked on 13 November 2026. A value that page does not state is shown as not stated.
We do not show prices, because they change often and differ between sellers. We also leave out Marstek's savings figures, which are theoretical values from its own model.
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Common questions about Marstek SATURN B2500-D
Can I use the Marstek SATURN B2500-D as a plug-in battery in my country?
It depends on local rules. Marstek markets it as a plug and play balcony system. 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 B2500-D need a micro-inverter?
Yes. It has two DC outputs of up to 400 W each and no AC output, so it feeds a micro-inverter that connects to your home.
How much solar can the B2500-D take?
Marstek lists two MPPT inputs of up to 800 W each, 12 to 59 V, up to 13.5 A each.
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.