AC/DC (Alternating Current/Direct Current)

What Do AC and DC Mean?

DC (Direct Current) always flows in one direction — this is what solar cells and batteries produce. AC (Alternating Current) periodically changes direction — in Europe at 50 Hz (50 direction changes per second). The electricity grid and household appliances use AC at 230 V.

Role in Photovoltaics

Component	Current Type	Voltage
Solar modules	DC	30—50 V per module
Module string	DC	300—600 V
Battery storage	DC	48—400 V
Inverter (output)	AC	230 V / 400 V
House grid	AC	230 V

The inverter is the central link: it converts the direct current from the modules into grid-compliant alternating current.

AC- vs. DC-Coupled Storage

• DC-coupled: The battery is charged directly from the DC string (one hybrid inverter). Fewer conversion losses.
• AC-coupled: The battery has its own inverter and is charged via the AC house grid. More flexible for retrofitting.

Practical Tip

On the DC side, a module string carries voltages of several hundred volts. This direct voltage is more dangerous than alternating voltage of the same magnitude. Therefore, DC wiring must be installed by qualified professionals.