Let's cut to the chase: A solar-powered 25 watts bulb could last anywhere from 4 hours to all night. Wait, no—that's oversimplifying. The actual runtime depends on three critical factors: In sunny California, a typical 100W solar panel generates about 400Wh daily. Larger systems with more capacity can provide backup for a longer duration, potentially supporting full. . But how long a battery will last during an outage depends on a few key factors, including your home's energy needs. LFP batteries can safely use 80-90% DoD, while lead-acid should stay at 50%. Size your battery for 1-3 days of autonomy for grid-tied systems, 3-5 days for off-grid applications. Generally, the higher the load power, the shorter the runtime; the lower the load power, the longer the runtime. Battery life usually ranges from 5 to 15 years based on your power consumption and charging practices. Formula: Charging Time (h) ≈ (Battery Ah × V × (Target SOC / 100)) ÷ (Panel W × (Eff% / 100)).
[PDF Version]
