How home batteries integrate with solar
Home battery systems store excess solar energy produced during the day for use when solar production is low or when utility prices are high. They add flexibility and resilience to a solar installation by shifting energy use from times of surplus to times of need.
Basic operation
- Daytime: Solar panels generate DC electricity. The system uses what the home needs first. Excess energy charges the battery instead of exporting all of it to the grid.
- Night or cloudy periods: The battery discharges to supply the home, reducing reliance on grid electricity.
- Backup power: In a grid outage, batteries can provide backup power for selected circuits or, in some systems, whole-house backup depending on capacity.
Key components
- Battery pack: Stores energy in lithium-ion or other chemistries.
- Battery inverter/charger: Manages charging/discharging and enables AC coupling with the home and grid.
- Energy management system: Controls when to charge or discharge based on solar production, time-of-use pricing and backup needs.
Coupling methods
- AC-coupled: Battery and solar each have their own inverters and connect to the home AC panel. This option is common for retrofits.
- DC-coupled: Solar and battery share a DC connection to a hybrid inverter, often more efficient for new systems and simplifies system control.
Sizing and usage
- Capacity: Measured in kilowatt-hours (kWh), it determines how long a battery can power loads.
- Power rating: Measured in kilowatts (kW), it limits how much load the battery can deliver at once.
- Use cases: Time-of-use bill management, backup power, self-consumption maximization and islanding during outages.
Considerations
- Round-trip efficiency: Energy lost in charging/discharging affects savings.
- Warranty and cycle life: Check how many cycles and what capacity the warranty guarantees over time.
- Incentives and policies: Some regions offer rebates or demand-charge reductions that change economics.
Working with an installer to model your load profile, solar production and backup needs will help size the battery and choose the right coupling approach for your home.