AC Coupled

AC coupling is a system configuration where solar panels and battery storage are connected through the AC (alternating current) side of the electrical system. In an AC-coupled setup, the solar array has its own inverter (converting DC to AC), and the battery has a separate inverter/charger that converts AC back to DC for storage and then back to AC when discharging.

AC coupling is the most common method for adding battery storage to an existing solar system. Since the solar panels already have their own inverter, a battery with a built-in inverter can simply be connected to the home’s AC electrical panel — no need to rewire the solar array. This makes AC coupling ideal for retrofits. Popular AC-coupled batteries include the Tesla Powerwall and Enphase IQ Battery. The slight downside is a small efficiency loss from the double conversion (DC → AC → DC → AC), typically around 5–10%. The alternative, DC coupling, connects the battery directly to the solar panels on the DC side, which is slightly more efficient but requires a compatible hybrid inverter and is more common in new installations designed from scratch.