Marstek Venus E 3.0 review: an affordable way to store electricity
21.8.2026
Translation: Megan Cornish
The Marstek Venus E 3.0 energy storage system’s been collecting excess electricity from the solar panels on my roof in my basement since May. It works alongside my smart home system to reduce my electricity costs.
Battery storage systems are booming, both for households and in industry. The reason’s clear: solar panels often produce more electricity than is needed at the time, especially around midday. And with a storage system, you can essentially save it for later or sell it when it’s expensive. For some companies, this is a business model in itself.
As a homeowner with a small photovoltaic system (9.5 kilowatts peak output) on the roof, I won’t get rich. But I want to use as much of the electricity I produce myself as I can. This relieves pressure on the grid – and lowers my electricity bill a bit.
When my PV system was installed around five years ago, storage systems were still very expensive. Since then, prices have dropped considerably. The Marstek Venus E 3.0 boasts real value for money. For under 1,500 Swiss francs, you get a battery storage system with a capacity of 5.2 kilowatt-hours (kWh).
The Swiss importer of this Chinese bargain provided me with a sample for testing purposes. As always with tests conducted by the Galaxus editorial team, this was done without any influence or obligation regarding how the test should be carried out or the result.
Installation without an installer
The price makes the Marstek storage system attractive, but there’s another reason. I can get it working without having to hire an electrician. That can easily add a few hundred Swiss francs to the cost. The Venus E 3.0’s a plug-and-play storage system. You just plug it into a free socket, and off you go. The control unit’s integrated, including a bidirectional inverter. You need this to either store electricity or feed it back into your home’s grid.
First, though, the unit needs to be installed in the right place. Mine’s in the basement. You could also set it up in the garage or even outdoors – it’s IP67 certified, meaning it’s dust-proof and protected against sprayed water. So, even if it’s pouring with rain, the storage unit won’t be affected. On delivery, it weighs around 60 kilogrammes including the packaging; don’t try to carry it on your own. Once it’s unpacked, the Venus E 3.0 is surprisingly slim and compact: 50 centimetres wide, 63 centimetres high and just 15 centimetres deep.
In my basement utility room, the inverter for the PV system’s already installed, the energy management system (EMS) is mounted in the fuse box and the upgraded boiler’s doing its job. The Marstek storage unit should fit right in. I’m placing it on the floor, but you can also mount it on the wall using the rail provided – heavy-duty anchors are also included.
The package includes a total of one cable, which fits one port on the Venus E 3.0. There’s a standard wall plug at the other end. It’s foolproof.
Connecting to the Solar Manager
For the Venus E 3.0 to know when the rooftop solar panels are generating more electricity than is currently being used in the house, it needs access to the total energy readings. During installation, the Marstek app detects the Wi-Fi network, requests the password and connects. Then, it locates and connects to the Shelly in the distribution box, which provides consumption and production data.
Sounds almost too easy, doesn’t it? It is. Because despite successful Wi-Fi integration and Shelly connection, the storage system isn’t working. The numbers in the Marstek app stay at zero. The only thing I can see is that the storage system has an initial charge level of 47 per cent. The Marstek storage system’s also recognised as a device in the Solar Manager app, but it’s not functional. Apparently, there’s no connection.
After an hour of fiddling with the settings, I gave up. I contacted Hans Fischer, one of the inventors of the Solar Manager. Surely he’d know. And lo and behold: less than ten minutes after my e-mail, he replied with the solution. You need an ethernet connection. Marstek blocks the Wi-Fi connection to the Solar Manager. I followed a brief guide, and as soon as I plugged a LAN cable into the port on the Venus E 3.0 and my switch, the Solar Manager confirmed the storage system was «connected». Incidentally, the ethernet requirement is also mentioned on the Solar Manager website(website in German). I should have just looked.
Marstek storage system users are reporting setup problems in online forums. An unstable Wi-Fi connection’s often the culprit – the module used by Marstek apparently doesn’t offer the best performance. A wired connection definitely has its advantages. Installation is generally straightforward, but a little technical understanding helps. You can find a good list of potential problems and solutions here.
Charging and discharging
My first test of the battery storage system is in May, with alternating sunshine and cloudy skies. The Marstek storage system immediately switches to charging mode. It draws 600 watts of the excess solar power supplied by the PV system and stores it in its LiFePO₄ battery. If clouds move in front of the sun, the controller reacts almost every second and reduces the current flow to the battery. There’s virtually no latency.
The manufacturer promises a lifespan of 15 years, or 6,000 full charge and discharge cycles. The warranty lasts for ten years. My internal calculator tells me that with a capacity of five kWh, at least 30,000 kilowatt-hours will pass through the storage unit in the coming years.
Is it worth it financially? At 1,500 Swiss francs, we can do a rough calculation, relating the investment to the kilowatt-hours. If you can save five cents on every kWh transaction, the purchase pays for itself.
That’s easily possible. If I store one kWh of solar energy, I lose the feed-in tariff from my electricity supplier, which is currently around ten cents. But if I use that one kWh in the morning to make coffee and tea, I save the 25 cents I’d otherwise have to pay. Simply put, the difference is my profit.
Marstek storage systems can also provide emergency power
I don’t want to have to think about how this difference will affect my electricity bill every time I make coffee. So, I let the system do the thinking for me. The Marstek app has four modes: Self-Consumption, AI Optimization, Manual and UPS. The latter’s useful if the storage system’s intended for emergency power. In Uninterruptible Power Supply mode (UPS for short), it charges whenever electricity’s available – whether from the grid or the solar panels on the roof. It essentially stores electricity whenever it can. Side note: this is one of the main reasons why energy storage systems such as the Marstek are currently in high demand in Ukraine, where Russian attacks repeatedly disrupt the power supply. Fortunately, this isn’t an issue in Switzerland or Germany. Nevertheless, it’s good to know that the Venus E 3.0 has a power socket I can tap into if we suffer a power cut.
In the other modes, I can manually set when charging and discharging are allowed very precisely. In AI mode, I could use dynamic tariff models with prices changing every 15 minutes to buy electricity at a very low price and then feed it back into the grid – i.e. sell it – when prices are high. However, this isn’t currently practical in Switzerland because dynamic tariffs are still in their infancy here and the price differences are too small. There are more opportunities in neighbouring countries. In some, you even get paid at certain times for taking surplus electricity.
Goal: use as much electricity at home as possible
My focus is on using as much of the generated electricity as possible, which involves my electric car charging station in the garage, my heat pump and my boiler. All of this already runs through my EMS, the Solar Manager. That’s why I control the storage system with it instead of the Marstek app. I don’t have to sacrifice any functionality. On the contrary, there are other modes available.
My 600-watt problem
Admittedly, though, this variety’s a bit overwhelming. The Eco mode immediately appeals to me. It’s supposed to charge the battery efficiently in line with usage and protect it by reducing power input during peak midday hours. Do I need that?
And then there’s the question of the maximum watts I can pump into the Marstek. Initially, I set it at 600 watts for both charging and discharging. Feeding more power into the grid isn’t allowed in Switzerland (page in German).
But I was probably too cautious. Anyway, Hans Fischer also suggested I increase the charging power for the battery. At 1,500 watts, the Venus E 3.0 is fully charged in just over three hours. That also makes Eco mode a good idea.
Curiosity gives way to yield
For the first two or three days, I’m on my phone a lot. I have to check the battery level, I have to see how many watts are currently being fed into the storage system, I want to know how much electricity was used the previous night. It’s fascinating. I could also sit in front of the storage unit in the utility room and watch the LED strip. If the light pulses from left to right, the battery is charging; from right to left, it’s discharging. There’s something meditative about it. You can turn the LED display off if you want to.
After a few days, my initial curiosity subsides. I now have enough confidence that the storage system’s doing what I expect it to. And the Solar Manager app confirms this. It sends me a push notification informing me that our household’s self-sufficiency and self-consumption rates have increased.
May’s drawing to a close. In the coming weeks, temperatures in Switzerland will start to climb, as will the number of hours of sunshine. The Marstek system’s often already fully charged by late morning. I’m considering whether to buy a second unit.
The five-kilowatt-hour capacity’s enough to last through the night on a lot of summer days when only the air conditioning and a few devices on standby in the house are using power. For several days in a row, we don’t draw a single kilowatt-hour of electricity from the grid. With a second battery, we could have even more self-sufficient days.
In a nutshell
Perfect starter storage
It really couldn’t be easier. The Marstek storage system’s a great option if you have a PV system – whether it’s on your roof or just a few modules on your garden shed or balcony. It’s easy to install, doesn’t take up much space and the Marstek app makes it easy to control. The Solar Manager solution I use is completely optional.
Pro
- Good value for money
- Fast response time between charging and discharging
- Free, easy-to-use app
- Easy to install
- Can be wall-mounted
- Doesn’t take up much space
Contra
- Pretty unstable Wi-Fi
Martin Jungfer
Head of Content
Martin.Jungfer@digitecgalaxus.chJournalist since 1997. Stopovers in Franconia (or the Franken region), Lake Constance, Obwalden, Nidwalden and Zurich. Father since 2014. Expert in editorial organisation and motivation. Focus on sustainability, home office tools, beautiful things for the home, creative toys and sports equipment.
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