At PlugInSolarEnergy, we regularly receive questions about the 800W limit that you find with plug-in home batteries and plug-in solar panels. This limit keeps reappearing in manuals, on product pages, and in online forums. But where does it come from? Is it a legal obligation? And are there alternatives? In this blog post, we will explain it clearly to you.
In short: the 800W limit applies to discharging, not charging. It is not a law, but a safety recommendation that manufacturers adhere to. And on a dedicated circuit, the power can often be much higher.
Why exactly 800 Watts?
A wall socket and the circuit behind it are designed to consume electricity: from the meter box to your appliances. With a plug-in home battery and solar panel, it sometimes works the other way around: they supply power back to the circuit.
Suppose you have a circuit with a 16A circuit breaker. It can supply a maximum of 3,680 Watts (16A × 230V). Your microwave, kettle, and lighting together consume 3,200 Watts. No problem. But what if your Marstek Venus E supplies an additional 800 Watts? This power does not go to the grid, but to the other appliances on the same circuit. The wiring now transports 4,000 Watts, while the circuit breaker only registers 3,200 Watts from the grid. The circuit breaker does not trip, but the cables are subjected to a heavier load than intended.
800 Watts (approximately 3.5 Amperes) is the margin that manufacturers use to limit this risk. It is not an exact science, but it is the figure that the industry has settled on as a safe upper limit for plug-and-play use.
Charging vs. discharging: an important distinction
The 800W limitation applies exclusively to discharging, not to charging. Why? Because both processes work fundamentally differently.
When charging, the battery draws power from the grid. This current flows through the circuit breaker, just like with any other appliance. If the Marstek Venus E draws 1,500 Watts and your other appliances consume 2,500 Watts, the circuit breaker sees 4,000 Watts and trips. The system works as intended.
When discharging, the battery adds power to the circuit. This current does not flow through the circuit breaker. Therefore, the protection does not see what is actually flowing through the cables. That is precisely why the Marstek Venus E can charge at 1,500 Watts or more, but discharging is limited to 800 Watts.
Is the 800W limit a legal obligation?
No. The 800W limit is not a law, but a practical standard adopted by the industry. The NEN 1010 standard stipulates that feeding back via a socket is not permitted, but this standard primarily targets installers. For consumers who connect a plug-in battery themselves, it is legally a grey area.
What is mandatory: registering your home battery via energieleveren.nl. This applies to every battery, regardless of its power output.
Do you want more than 800 Watts? These are your options
1. Dedicated circuit, same plug: Many batteries, including the Marstek Venus E, can be unlocked to a higher discharge capacity via the app, provided they are on a dedicated circuit. You confirm a disclaimer in the app, and the responsibility lies with you.
2. Combine multiple units: Place multiple Marstek Venus E batteries on separate circuits. Two units on separate circuits? Then you can discharge 2 × 800 Watts = 1,600 Watts. Each additional unit adds 800 Watts to your total discharge capacity.
3. Fixed connection by an installer: In this case, the battery falls under regular installation standards, and the 800W limitation is completely waived. More expensive, but also the most robust solution.
What are the risks if you ignore the limit?
Ignoring the 800W limit on a shared circuit carries serious risks:
• Overheating of cables: Consistently too much current can damage the insulation of wiring. This builds up over months or years, so the danger only becomes noticeable when it's too late.
• Melting contacts: Sockets and connection terminals can deform due to prolonged overload. A slight burning smell from the socket is an alarm signal to intervene immediately.
• Insurance problems: In case of damage, your insurer may refuse coverage if it turns out that the battery was not connected in accordance with regulations. An additional reason not to underestimate this.
Hiring an installer for a dedicated circuit typically costs between €150 and €300, depending on the situation. A small investment that prevents a lot of problems.
Conclusion
The 800W limit is not a law, but a safety limit that manufacturers like Marstek apply for plug-and-play use on a shared circuit. For most households, 800 Watts is more than sufficient to power the refrigerator, TV, lighting, and other basic consumers.
Do you want more power? Connect the Marstek Venus E to a dedicated circuit and unlock the higher power via the app.
Do you have questions about the Marstek Venus E or our other products? Feel free to contact us at info@pluginsolarenergy.be, we are happy to help you!