4 Modules on an 800W Inverter: How a storage system prevents curtailment (throttling) in summer.

4 Modules on an 800W Inverter: How a Storage Unit Prevents Curtailment (Throttling) in Summer.

Since the Solarpaket I came into force, the landscape for balcony power plants in Germany has fundamentally changed. It is now officially permitted by law to connect solar modules with a total output of up to 2,000 watt-peak (Wp) to an inverter whose feed-in power to the household grid is limited to 800 watts (VA).

This new freedom excites many owners of plug-and-play solar systems, but it raises a massive technical question just in time for summer. If the sun is directly overhead in June or July and the four installed modules together easily generate 1,500 watts or more, but the inverter legally limits output to 800 watts – what happens to the remaining 700 watts? Are they discarded unused? How can this valuable energy be saved?

The answer to this dilemma lies in the intelligent combination with a battery storage system. In this detailed guide, we explain how you can avoid summer curtailment, why modern storage systems like the Growatt Noah 2000 are ideal for this, and how you can get the maximum out of your system through smart wiring.

Why does the inverter curtail output in summer anyway?

The phenomenon of curtailment (often also referred to as throttling or "clipping") is a purely technical and legal necessity. A micro-inverter for balcony power plants converts the direct current (DC) from the solar modules into grid-compliant alternating current (AC).

If your module output exceeds the maximum output power of the inverter, the following happens:

• The inverter deliberately moves its operating point (the so-called MPP track) out of the optimum.

• It increases the internal resistance so that the modules deliver less current than they physically could.

• The excess energy remains unused as heat in the solar module.

Without a storage unit, an enormous amount of free electricity is wasted on every sunny summer day between 10:00 AM and 4:00 PM. The more you "oversize" your system (e.g., by installing 4 modules of 430 Wp each), the more painful this loss becomes.

How does a storage unit prevent thermal clipping?

A modern balcony power plant storage unit is physically installed between the solar modules and the inverter. This fundamentally and elegantly changes the energy flow in summer:

1. Modules deliver full load: The four solar modules produce, for example, 1,500 watts of direct current under bright sun.

2. The switching in power management: The intelligent control unit of the storage unit splits this energy flow.

3. 800 watts for the house: Exactly 800 watts (or less, depending on your set base load) are forwarded directly to the micro-inverter so that it supplies the household grid.

4. 700 watts for the battery: The remaining surplus of 700 watts does not flow into the inverter, but is redirected directly into the lithium iron phosphate (LiFePO4) cells of the storage unit.

Through this DC-side intermediate storage, the inverter never sees more than the permitted 800 watts. The modules can fully breathe and produce exactly as much energy as physics allows. You can avoid curtailment and simply use the same electricity in the late evening or at night.

The importance of MPPT inputs with 4 modules

Anyone who wants to operate four modules efficiently quickly encounters the term MPPT (Maximum Power Point Tracker). An MPPT is the electronic brain circuit that constantly searches for the optimal voltage to extract maximum power from a module.

If you want to connect four modules to a power management system, two paths are open to you:

Series or parallel connection to standard inputs

Many older storage units only have one or two MPPT inputs. This means you have to connect two modules in parallel or in series. This has disadvantages in summer: If a module is shaded by a balcony railing or a cloud band, the output of the parallel-connected twin module often also drops. In addition, voltage and current limits ($V_{max}$ and $I_{max}$) must be strictly adhered to to avoid damage.

The premier class: Systems with dedicated inputs

Modern storage solutions of the latest generation were developed precisely for the 2,000 Wp scenario. An outstanding example on the German market is the Growatt Noah 2000. This storage unit features an integrated system specifically designed for high input power. Combining such storage units with inverters that have 4 MPPT inputs (such as the popular Hoymiles HM-1600/HMS-1600, which has been throttled to 800W), benefits from absolutely independent control of each individual module.

Each of the four modules operates at its own optimum – regardless of whether one is oriented southeast, two south, and one southwest. Shading on module 1 has no influence on modules 2, 3, and 4.

The interaction in practice: A summer day in profile

To illustrate how effectively this setup works, let's consider the typical curve progression on a cloudless July day with a 4-module system (1,700 Wp total output) and a 2 kWh storage unit:

• 8:00 AM: The sun rises. The modules deliver 400 watts. Since the house is in standby, 150 watts flow into the grid, 250 watts charge the battery.

• 12:00 PM: Peak time. The modules are hot and deliver 1,500 watts. The inverter constantly delivers its legal 800 watts to the house. The remaining 700 watts flow into the battery with maximum efficiency. Without storage, the curve would have been radically cut off at 800 watts here.

• 3:00 PM: The battery is fully charged (100% SOH). From now on, the system inevitably curtails the input power of the modules, as the energy has nowhere else to go – unless major consumers are running in the house.

• 7:00 PM: The sun sets. The modules deliver only 50 watts. The storage unit seamlessly kicks in and feeds the required base load (e.g., 200 watts) from the energy saved during the day.

What to consider when buying and installing? (EEAT safety note)

From an electrical engineering perspective, the "oversizing" of balcony power plants is absolutely safe, provided that manufacturer specifications are adhered to.

• Observe short-circuit current ($I_{sc}$): When connecting modules in parallel, the current (amperes) adds up. Be sure to check whether the inputs of your storage unit or inverter can handle the maximum short-circuit current of the modules. The Growatt Noah 2000, for example, is explicitly designed for high currents, which makes it a safe bet in system design.

• Maintain voltage limits ($V_{oc}$): In a series connection, the voltage adds up. If the maximum input voltage of the storage unit is exceeded even briefly in winter during extreme cold (where solar modules generate higher voltages), this irreversibly destroys the electronics.

Conclusion: Is upgrading to 4 modules with storage worthwhile?

The combination of four modules and an intelligent storage unit is the economic premier class of balcony power plants. It eliminates the biggest annoyance of Solarpaket I: unused solar power in summer.

By specifically avoiding curtailment, you maximize your self-sufficiency rate from typically 30 percent to up to 85 percent. Thanks to modern storage components and inverters with up to 4 MPPT inputs, installation is now safe and efficient for even laypersons via Plug & Play.

Frequently Asked Questions (FAQ)

1. Is it legal to connect 4 modules with a total of 1,800 Wp to an 800W inverter?

Yes, this is absolutely legal since 2026. Solarpaket I stipulates that the installed module power (DC side) may be up to 2,000 Wp. The only hard limit relevant for classification as a permit-free balcony power plant is the AC output power of the inverter, which must be capped at exactly 800 watts. How many modules you use to achieve or buffer these 800 watts is up to you.

2. Does the high module output of 1,500W in summer harm the 800W inverter?

No, as long as the maximum input voltage ($V_{max}$) of the inverter is not exceeded. An inverter only "draws" as much current (amperes) as it needs for its maximum operating power of 800 watts. The modules do not actively "push" current into the device. However, if you connect a storage unit in between, the inverter is relieved anyway, as the storage unit intercepts the excess energy before it reaches the inverter.

3. What happens if the storage unit is completely full by midday at 1 PM in summer?

If the storage unit is 100% charged and no major consumers are running in the house, physical curtailment takes effect subsequently. The power management then throttles the power consumption of the modules, so that only the 800 watts (or less) required for the inverter are generated. To prevent this, it makes sense to schedule energy-intensive processes (such as the washing machine or dishwasher) for exactly the midday hours using smart socket timers.

4. What is the advantage of the Growatt Noah 2000 in a 4-module setup?

The Growatt Noah 2000 is characterized by very high flexibility in input power. It has two separate MPPT channels, each of which can be loaded with up to 900 watts (i.e., a total of 1,800 watts of module power). Thanks to Y-splitters, four modern 430Wp modules can be easily connected in pairs without the system being thermally overloaded or valuable energy being lost due to overly tight current limits.

5. Can I upgrade an old 600W inverter to 800W via software to reduce curtailment?

That depends entirely on the model. Many modern micro-inverters (e.g., from Hoymiles, Deye, or TSUN) delivered with 600 watts in 2024 and 2025 are already based on the 800-watt platform hardware-wise. These can be conveniently unlocked to 800 watts free of charge via the manufacturer's official app or the DTU interface. However, older pure 600W models cannot be upgraded via software, as their internal components (capacitors, transformers) are not designed for the thermal load of 800 watts.