Hybrid inverters are combination devices that contain a grid tied solar inverter and at the same time a battery inverter for managing a storage battery.
For example, the devices from Alpha OutBack SPCIII 5000 and 7200 can run alone with any energy source, but the devices can only feed into the house network and not into the public grid. The connected phase of the public is led through the device in series and supplies your consumers at the output. For physical reasons it cannot go in the other direction.
Most devices, however, are connected in parallel to the grid, i.e. the current can flow in both directions through the cable.
Single-phase hybrid inverters are available from approx. 1.5 kW to 4.6 kW, three-phase mostly from 4.6 (5.0) kW.
It should also be noted that some of the hybrid inverters can be connected in parallel to double the output or e.g. to triple. That means e.g. two hybrid inverters with 8 kW each charge a storage unit with 16 kW or supply the consumers with this power. One device is the master, the second follows it.
Emergency power, backup power or island operation
If the inverter is to continue to run even if the public grid fails, the regulations in Germany require that the house grid with battery storage is disconnected from the public grid.
Many manufacturers such as SMA, Fronius, Kostal, Solax or Solarmax refer to so-called switch boxes from Enwitec, which work with their inverters in accordance with the rules and separate the house from the public grid. The price for a switch box is approx. 1000 Euro.
Other manufacturers such as Kako or Growatt have their own switch in their range that cost significantly less. The battery inverters type II from Victron Energie have this compliant ENS already built into the device. These battery inverters allow a connection in parallel to the mains as well as in series.
However, many of these hybrid inverters are not built for permanent island or off-gid operation for years.
Only the Sunny Island battery inverters from SMA (industrial quality), the battery inverters from Victron Energy and AlphaOutback and maybe also the pure battery inverters from Growatt are actually 100% Island- or Off Grid-capable.