Maximum current per residual current device: this is how it works according to NEN1010

According to NEN1010, an installation or residual current device may only be continuously loaded up to 80% of its nominal value. In this article, you will find a handy table with the maximum continuous current per fuse rating. We also explain why the main connection plays an important role in this. Essential for a safe and compliant PV or battery system installation.

Note: for battery systems, the fuse is chosen based on the inverter power, not the power of the battery itself.

Why is the 80% rule so important?

When designing a safe electrical installation, it’s about more than just the right materials. The sizing must be correct.

The NEN1010 standard prescribes that devices must not be continuously loaded up to 100% of their rating.

The rule of thumb is:

A maximum of 80% of the nominal rating of the device may be continuously loaded.

This prevents overheating, increases reliability, and extends the lifespan of your installation.

This rule applies, among others, to:

• ✅ Residual current devices

• ✅ Installation circuit breakers

• ✅ Circuits in homes and commercial buildings

Handy table: maximum current per device (80% rule)

Use this table to see at a glance which continuous current you can safely run through a fuse:

Practical example: connecting an inverter or battery

Suppose you install an inverter that can supply a maximum of 40A. Then you need a residual current device of at least 50A (50A × 0.8 = 40A). If you choose a lighter device, you risk unwanted disconnection or even damage to the installation.

💡 Note: this also means that your main connection must be at least 3x63A.
(63A × 0.8 = 50.4A → needed to safely apply that 50A device)

Don’t forget the main connection

Not only the individual devices must comply with the 80% rule. The main connection of a home or building must also have sufficient capacity to safely support all connected systems.

Why this is important:

1. Selectivity

When the devices behind the main connection are heavier than the main fuse, this can lead to undesirable situations. In case of a fault, not only the relevant circuit will switch off, but possibly the entire installation – that is, the whole house or building.

⚠️ This is obviously undesirable and can easily be prevented by correct sizing and selective coordination of main and group devices.

2. Overload

Every component in an installation is designed for a maximum current capacity. With solar panels, batteries, and bidirectional charging stations, internal current circulation can occur. This means that more current circulates within the system than the main fuse would normally supply to the building.

This is often overlooked.

Example situation:

A home with a 3x25A connection (max. 17,250 W) has at a peak moment:

• 15 kW going to an electric car

• 4 kW going to a heat pump

That is a total of 19 kW, which the grid connection cannot supply. But suppose 5 kW of this power comes from a battery or PV system, it seems as if everything works fine — but internally the busbars and components can still become overloaded if they are not sized for this. So pay close attention here! 

Situations you may encounter:

• The end user wants to expand:

  • Request a capacity increase from the network operator in time

  • Or choose load balancing or peak shaving
    (commonly used in commercial projects where upgrading is not an option)

• Battery systems as a solution:

  • These can cleverly absorb peaks and reduce grid congestion

  • A battery can even prevent the need for an expensive grid upgrade

🔗 Interested in smart energy management? Check out the possibilities at 4blueprint or contact us.

⚠️ Note: make sure that all components in the distribution board – including busbars – are suitable for the extra load from inverters, batteries, and other sources. This way you prevent overload, voltage drop, or thermal damage.

Common mistakes in practice

❌ Ignoring the 80% rule because "it worked fine before"
❌ Overloading a circuit by combining multiple consumers
❌ Forgetting the main connection & components when expanding the system

At 4blue, we believe that knowledge and quality make the difference between just installing and delivering real craftsmanship. That’s why we like to help you as an installer with the right information, products, and support.

Conclusion

The 80% rule from NEN1010 is not a theoretical detail, but an essential part of every safe installation. With the table in this article, you can quickly and easily determine which device is suitable for your system.

And don’t forget: the main connection plays a crucial role in this. Especially with combinations of PV, batteries, and charging stations.

✅ Safe
✅ Compliant with the standard
✅ Ready for the future

CTA – Everything you need for safe installations

Check out our range of AC materials immediately, including residual current devices, installation circuit breakers, cables, and much more!