What happens after sunset
In a standard grid-tied system without a battery, the inverter stops producing and the home imports electricity from the utility. The transition is normally automatic and invisible. Daytime exports may create bill credits, but the value of those credits depends on the utility tariff.
Do not assume every exported kWh offsets a later imported kWh at the retail rate. Net billing, time-of-use prices, non-bypassable charges and annual true-up rules can change the value.
Why rooftop solar shuts down in an outage
Most grid-tied systems shut down when the grid fails to prevent energizing utility lines. Daylight alone does not guarantee backup power. Islanded operation requires compatible inverter controls, transfer equipment and a protected-load design; many systems also require a battery.
Ask an installer to identify exactly which circuits remain powered, the continuous and surge limits, and whether solar can recharge storage while islanded.
Battery storage after dark
A battery shifts daytime energy into evening or outage hours. Capacity in kWh affects runtime; power in kW affects which loads can run together. Whole-home air conditioning, electric heat, water heating, pumps and EV charging can exceed the power or energy of a small system.
Build a critical-load list and use measured energy where possible. Product model, quantity, operating reserve and weather determine real runtime — not a generic “one battery powers a home” claim.
Moonlight and cloudy weather
Moonlight is reflected sunlight but is far too weak for meaningful household production from conventional rooftop panels. Cloudy daylight is different: panels still produce, but output can vary widely with cloud thickness, season and system design.
Use monitoring data or a weather-based model instead of a fixed cloudy-day percentage. For backup planning, include multiple low-production days rather than assuming the battery fully recharges every morning.