Adding a battery to plug in solar you already have

Three ways to add a battery

A DC coupled battery sits between the panels and the micro inverter. Anker describes its first Solarbank E1600 this way, and Zendure's AIO 2400 has no inverter of its own: its data sheet lists two outputs to an external micro inverter with up to 1,200 W in total. An all in one unit such as the Anker Solarbank 2 E1600 Pro or the EcoFlow Stream Ultra contains its own inverter and takes the panels directly. An AC coupled battery such as the EcoFlow Stream AC Pro has no solar input at all: it plugs into a socket and charges from the surplus your existing system produces.

Read: is a balcony battery worth it?

Can your micro inverter stay?

With a DC battery, yes, if it is compatible. Anker says the Solarbank E1600 works with micro inverters that accept 11 to 60 V, naming Deye, Hoymiles and APsystems, and does not support string inverters. Check the voltage range and power of your inverter against the battery's data sheet before you buy. With an all in one unit, the old inverter is no longer needed: the German consumer advice centre writes that such a unit replaces it, which also saves the compatibility check. With an AC battery the existing system stays as it is. EcoFlow says the Stream AC Pro works with any micro inverter, since it connects through a wall socket.

Read: power station or balcony battery?

The 800 W limit with a battery

In Germany, section 8 (5a) of the Renewable Energy Act covers one or more plug in solar devices with a total inverter power of up to 800 VA behind one connection. A DC battery or an all in one unit changes nothing here, as long as one inverter of at most 800 VA feeds the grid. An AC battery brings a second inverter, and the Stream AC Pro is rated at 800 W towards the grid on its own. The law text does not say how a battery's inverter is counted, so set the system up so that the combined feed in stays within 800 W, and ask your grid operator.

In Belgium, the consumer guide Selectra gives 800 W per household, panels and batteries together. Synergrid adds two points: an inverter to which batteries can be connected on the DC side must also be approved for storage, and since 15 October 2025 a battery needs a power control system, either the EnFluRi sensor or the P1 port of the digital meter. Look up the exact model on the C10/26 list before you order.

Battery rules by country

Registering the battery in Germany

A battery connected to the grid is a unit of its own in the Marktstammdatenregister. ADAC writes that it must be registered separately, and the consumer advice centre says that as a rule it must be registered. The regulation on the register sets one month after start for new units and one month for changes to data already entered, which matters if you replace the micro inverter with an all in one unit. Log in to the account you used for the solar device and add the battery there.

Whether the grid operator must also be told is disputed. ADAC says a standard plug and play battery up to 800 W no longer needs a separate notice, because the register passes the data on; other sources say the operator should be informed. The safe course is to register the battery and ask your operator.

Great Britain: batteries are not part of the plug in route

The government response of July 2026 states that the new plug in route applies only to solar devices without batteries and does not permit battery storage systems. Batteries sold in Britain that plug into a wall socket are therefore not covered by the new rules, whatever the product page suggests. In Great Britain, adding a battery remains a normal installation for a registered electrician.

Read: the UK rules since August 2026

Does it pay off?

A battery only stores what your panels produce beyond your own daytime use. The consumer advice centre notes that with a small system of two panels the economics are less attractive, suggests about 1 kWh of storage per 1,000 kWh of yearly consumption, and warns that oversized batteries cost more and are often not fully used. Compare models by the price per kWh they can store over their life, not by the price of the box.

Read: the price per stored kWh