Marstek VENUS E 4.0
A 5 kWh LFP battery with a 3 kW bidirectional inverter and 3 kW backup, expandable to three units through the Marstek SmartBox.
- Best for whole-home backup
- AC battery
- 5 kWh usable
- 3 kW output
- Made by Marstek.
- Capacity: 5 kWh usable, with LFP cells rated for over 10,000 deep cycles.
- Power: 3 kW bidirectional on-grid inverter and 3 kW backup power with a switchover under 10 ms.
- Expandable to three units through the SmartBox: up to 9 kW and 15 kWh.
- 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 E 4.0. The figures on this page come from the sources listed at the end of the page, checked on 10 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
5 kWh
Usable capacity
3 kW
Bidirectional power
10,000+
Deep cycles (Marstek)
Specifications
Last checked on 10 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. | 5 kWh usable |
| Battery chemistryLFP (lithium iron phosphate) cells are known for long life and stable behaviour with heat. | Lithium iron phosphate (LFP), 314 Ah cells |
| 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 deep cycles and a design life of more than 15 years |
| ExpansionExtra battery units that add storage to the same system. | Up to three units through the SmartBox, for up to 9 kW and 15 kWh |
| Power | |
| AC output, grid-connectedThe lower output allowed when it feeds power into the home's circuits or the grid. | 3 kW bidirectional on-grid inverter. Marstek does not state a lower default grid output on this page |
| Backup outputA separate socket that keeps selected devices running when the grid is down. | 3 kW continuous, switchover under 10 ms (EPS) |
| AC charging inputHow fast it charges from a wall socket or the grid. | Not stated in the sources we read |
| Efficiency and standby useLosses when charging, discharging and doing nothing. | Not stated in the sources we read |
| Solar | |
| Solar inputHow much solar panel power it accepts. A higher figure fills the battery faster on a sunny day. | Not stated in the sources we read |
| Grid connectionThe supply type it is built for. Check it matches your home's supply. | AC-coupled bidirectional inverter; works with Marstek, Shelly and P1 smart meters for anti-feed-in control |
| Connection and housing | |
| Dimensions (W × D × H)Check the space before you buy, including room around it for airflow and cables. | Not stated in the sources we read |
| WeightMatters for lifting, wall mounting and moving it. | Not stated in the sources we read |
| 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 (natural convection cooling) |
| ConnectivityHow you monitor and control it, usually through an app. | Wi-Fi, Bluetooth and LAN; Marstek app and an open API for third-party energy management platforms |
| Warranty | |
| WarrantyThe period the maker covers. Read the terms: conditions and capacity guarantees differ. | Not stated in the sources we read |
Compatible with
What Marstek says this product works with. Anything not listed here is not confirmed.
- Smart meters
- Marstek says it works with Marstek, Shelly, P1 and other mainstream smart meters.
- EV charging
- Integrates with the Marstek portable EV charger for scheduled charging.
- Expansion
- Up to three units through the Marstek SmartBox.
Rules where you live
Rules for plug-in batteries differ by country, and we could not confirm a UK version or plug. 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
- 5 kWh usable in one unit
- 3 kW bidirectional power and 3 kW backup
- Over 10,000 deep cycles per Marstek
- IP65 and under 30 dB
- Expandable to 15 kWh through the SmartBox
Worth checking before you buy
- Whether it counts as a plug-in product depends on your country: check the rules below
- Size, weight, efficiency and warranty are not on Marstek's product page
- Marstek does not state a solar input on the page we read
- Expansion needs the separate SmartBox
Change log
We record changes to this page here, so you can see when figures such as the warranty were last updated.
- 10 November 2026
- Page published. Warranty at publication: not stated on the Marstek product page. This page covers the VENUS E 4.0, not the VENUS E 3.0 or the VENUS E Mini.
Where this information comes from
We have not tested the VENUS E 4.0. Every figure above comes from Marstek's VENUS E 4.0 product page, last checked on 10 November 2026. The specification tab of that page showed no table, so size, weight, efficiency and warranty are shown as not stated. A value this page does not state is shown as not stated.
We do not show prices, because they change often and differ between sellers.
- Manufacturer Marstek VENUS E 4.0 product page
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Common questions about Marstek VENUS E 4.0
Can I use the Marstek VENUS E 4.0 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.
Is there a Marstek VENUS C?
We found no product of that name on Marstek's site. The VENUS E 4.0 is the newest VENUS plug-in battery there, alongside the VENUS E 3.0 and the VENUS E Mini.
How far can the VENUS E 4.0 be expanded?
Marstek says up to three units through the SmartBox, for up to 9 kW and 15 kWh.
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.