800 W Balcony Solar with a Battery: Design and Rules

A balcony solar system produces most of its power around midday, when many homes use little. A battery stores that surplus for the evening, so more of the solar energy is used at home instead of being exported for little or nothing. Technically, this is easy. The rules are less simple: the 800 VA limit for plug-in solar applies to what the system feeds into the home, not to battery size, and neither the German plug-in standard nor the UK plug-in route covers devices with storage.

How a battery works in a balcony system

There are three common ways to add storage to a small solar system. They behave differently, and the rules treat them differently.

DC-coupled units are the usual "balcony storage" products. The panels connect to the storage unit, which charges its battery and feeds the home through a single inverter. Because there is only one inverter, the AC output can be capped at 800 VA whatever the battery is doing. This is the design that fits best with a plug-in limit.

AC-coupled batteries sit beside an existing solar inverter and have their own inverter. The solar and battery outputs then add up, so two devices can together exceed 800 VA. In Germany only one plug-in solar device is allowed per household, so a second feed-in device on another socket is not a plug-in solution.

Hybrid systems with fixed wiring are ordinary home storage. They need an electrician and are registered with the network operator in the normal way. In return, they have no 800 VA limit tied to a socket and can provide proper backup power.

What the 800 VA limit does and does not cover

The limit is about AC output from the inverter, measured as apparent power. The DKE FAQ on DIN VDE V 0126-95 sets the maximum feed-in power of the inverter at 800 VA. There is no tolerance in this figure, so "800 W ±5%" is not the same thing.

The limit does not cap battery capacity. A 2 kWh or a 5 kWh battery can sit behind an 800 VA output. What changes with a larger battery is how long the system can supply the home at up to 800 VA, not how much power it delivers at once.

Two other limits matter for planning:

• Module power. German law counts a system as a plug-in solar device up to 2,000 W of module power and 800 VA of inverter output. With a household plug, DIN VDE V 0126-95 allows up to 960 W of module power. Above that, up to 2,000 W, a special energy socket installed by an electrician is needed.
• One device per household. The DKE FAQ states that only one plug-in solar device may be connected per household.

Sizing: how much battery makes sense

For one 800 W balcony kit, a battery in the range of about 1–2.5 kWh is usually enough. A simple example shows why:

1. On a clear summer day, 800 W of panels might produce around 4 kWh. The real figure depends heavily on direction, tilt and shading.
2. Part of that is used straight away by the home's base load: the fridge, router and devices on standby. A base load of 150 W uses about 1.2 kWh over eight daylight hours.
3. The remainder, perhaps 2–3 kWh on a good day and much less in winter, is what a battery could store.

A much larger battery mainly helps when there is more module power (up to 2,000 W), when it can also be charged from other sources, or when backup power is the goal. In spring, autumn and winter a large battery behind 800 W of panels will rarely be full. For backup power, larger batteries and higher outputs usually mean a fixed-wired system anyway.

Germany: where storage stands

Germany has the clearest rules for plug-in solar, but no finished rules yet for plug-in storage.

• The product standard leaves storage out. DIN VDE V 0126-95, published in November 2025 and applying from 1 December 2025, is the first product standard for plug-in solar devices. The DKE FAQ states plainly that the standard does not cover plug-in solar devices with energy storage, and that such devices must meet additional requirements. Committee DKE/K 373 has started planning a further part for storage. No publication date has been announced.
• Battery certification uses existing standards. Until that part exists, the battery side of a storage unit can only be assessed against the general standards for stationary batteries and their inverters.
• Register both units. Solar systems and batteries must be entered in the Marktstammdatenregister (MaStR) of the Bundesnetzagentur within one month of commissioning. A battery counts as a separate unit, even when it is part of a plug-in system.
• The simplified route is for systems without storage. For plug-in solar without storage, registration in the MaStR is enough; a separate notice to the network operator is no longer needed. The Verbraucherzentrale (consumer advice centre) says the simplified registration does not yet exist for devices with storage, and advises that the storage is connected by a qualified electrician and registered with the network operator.
• Tenants and owners. Since October 2024, landlords and owners' associations can refuse consent for plug-in solar only if installation would be unreasonable. Consent is still required.

In practice, many balcony storage units are already in use in Germany, and the standard does not ban them. But a seller cannot claim that a device with a battery complies with DIN VDE V 0126-95, because the standard does not cover it. The safest route today is a device whose AC output is limited to 800 VA, a battery certified to the relevant battery and inverter standards, both registered in the MaStR, and the connection done or checked by an electrician.

UK: storage is outside the plug-in route

Since 27 August 2026, plug-in solar can be connected to a 13 A socket in Great Britain, but only for solar PV without storage. The law defines a plug-in microgenerator as a device that is not designed to import energy to store it, the IPS lists plug-in solar devices integrated with batteries as out of scope, and Ofgem has said plug-in storage devices remain prohibited for now.

A battery in a UK home is therefore a fixed-wiring job: designed and installed by a competent installer under BS 7671 and notified to the distribution network operator (DNO) in the usual way. Do not market a balcony kit with a battery as a socket-connected product in the UK. Our article on plug-in solar in the UK covers the rules in detail.

Other European countries

Limits and procedures differ by country. Some allow higher plug-in outputs, some require a dedicated circuit, and many have no specific rules for plug-in storage yet. Before selling a balcony storage product in a new market, check the national grid-connection rules, the registration process and whether storage is treated as a separate system.

Checklist for distributors and installers

1. Know the design. Is the battery DC-coupled behind a single inverter, or does it add a second inverter? Only a single limited output keeps the system at 800 VA.
2. Check the AC limit. For the plug-in category in Germany, the inverter must limit the product's output to the home to 800 VA, with no tolerance.
3. Check the module power. Up to 960 W with a household plug; up to 2,000 W only with the special socket installed by an electrician.
4. Ask for battery certificates. These cover safety standards for stationary lithium batteries (such as IEC 62619) and transport testing (UN 38.3), plus grid-connection certificates for the inverter.
5. Do not overclaim. Do not describe a device with a battery as compliant with DIN VDE V 0126-95, and do not sell it as a plug-in product in the UK.
6. Explain registration. In Germany, solar and battery are registered in the MaStR within one month; for systems with storage, advise the customer to involve an electrician and the network operator.
7. Size realistically. For one 800 W kit, 1–2.5 kWh is usually enough; larger batteries make sense with more module power or for backup.

How VaySunic can help

VaySunic designs and manufactures microinverters, storage and chargers at its R&D and manufacturing centre in Wuxi, with headquarters in Germany. For small systems we offer two routes:

• Solar only, plug-in: the SolarKits plug-in balcony kit and the SolarCore P2 microinverter, including the 800 W model, for markets where plug-in solar is permitted.
• Solar with storage: PowerCube VA800D combines the inverter and a 2.5 kWh battery in one DC-coupled unit with an 800 W AC output. Its solar inputs accept more than 2,000 W, so keep the connected module power within the limits that apply on site. It can be expanded with VB5000D packs installed by a qualified electrician. For larger homes, the VA2000D to VA3000D models and the SolarHub hybrid microinverter work as fixed-wired home storage with backup power.

Because the rules for plug-in storage differ by country and are still developing, we recommend that systems with a battery are connected or checked by an electrician. Contact us for the current certificates of a specific model in your market, or see our distributor programme.

Sources

• DKE, FAQ on DIN VDE V 0126-95 (published 17 December 2025)
• Verbraucherzentrale, Gesetze und Normen für Steckersolar: Was gilt, was gilt (noch) nicht? (March 2026)
• Verbraucherzentrale, Marktstammdatenregister: Das müssen Sie bei Solaranlage und Co. wissen
• balkon.solar, Neue Steckersolar Norm (November 2025)
• pv magazine Deutschland, VDE veröffentlicht Produktnorm für Stecker-Solar-Geräte (November 2025)
• DESNZ, Plug-in Solar Device Interim Product Specification, Version 2.0, July 2026 (PDF)
• Ofgem, Decision to approve DCRP/MP/26/02: amendment to G98 to facilitate plug-in microgeneration, 11 August 2026 (PDF)