How batteries work with rooftop solar
Batteries store excess solar energy generated during the day so it can be used later—during evenings, overnight, or outages. Integrating batteries with solar changes system design, adds components, and provides flexibility for energy use and backup power.
Integration approaches:
- AC-coupled systems: Batteries connect on the AC side with a separate inverter/charger. They’re easy to retrofit to existing grid-tied systems.
- DC-coupled systems: Batteries connect on the DC side, allowing more direct energy flow from panels to storage before inversion. This can be more efficient for certain designs.
- Hybrid inverters: Combine PV inverter and battery management in one unit for compact and coordinated operation.
Benefits of adding batteries
- Backup power during grid outages (depending on system configuration and capacity)
- Time-shifting solar energy to use during peak-rate periods or overnight
- Increased self-consumption and reduced reliance on the grid
Considerations and trade-offs
- Cost and payback: Batteries add significant cost, and payback depends on electricity rates, incentives, and usage patterns.
- Sizing: Battery capacity is measured in kilowatt-hours (kWh); sizing depends on desired backup duration and load profile.
- Lifecycle and maintenance: Batteries have cycle life limits and may need replacement after several years.
Batteries enhance resilience and flexibility, and they pair well with smart energy management to optimize when to charge, use, or grid-export stored energy.