Will rooftop solar keep your home on during a power cut?
Understand the difference between grid-tied solar, hybrid inverters and battery backup before estimating panel and storage size.
A solar panel and a backup system solve different problems
Panels produce energy when sunlight is available. A battery stores energy for later. An inverter converts DC electricity to the AC used by most household appliances. A grid-connected solar installation can reduce grid purchases, but a basic grid-following inverter generally disconnects when the grid is absent for safety.
If you need power during an outage, confirm that the complete system is designed to supply backup: this may require a hybrid or backup-capable inverter, appropriate switching/islanding protection, and often storage. Product labels such as “solar ready” do not prove a system will energize your home during an outage.
Size storage for energy and power
Estimate the essential AC energy needed during the expected outage. Then account for the battery’s permitted usable fraction and conversion losses: nominal storage ≈ AC energy ÷ inverter efficiency ÷ usable fraction. Check the battery and inverter datasheets because allowed discharge and efficiency vary with model, temperature, age and load.
Separately check maximum simultaneous watts and motor start-up surge. A battery can contain enough kWh but still be unable to deliver the required kW. The NREL storage overview explains why power, energy, state of charge and efficiency are distinct battery attributes.
Estimate a panel rating as an early screen
A rough first-pass equation is required daily charging energy ÷ (equivalent peak-sun hours × overall system factor) = panel watts. If a battery needs 3 kWh and you assume 5 equivalent full-sun hours and a 75% overall factor, the arithmetic gives about 800 W of PV nameplate capacity.
That is not a site-specific generation forecast. Shade, orientation, tilt, temperature, season, dust, wiring, inverter limits and the actual charging window change output. “Peak-sun hours” is an equivalent-energy measure, not a promise of that many hours at full panel output.
Check system behavior before buying
Ask the installer to show which circuits are backed up, how the system isolates from the grid, which loads can run together, and what happens when the battery is empty. Confirm the permissible battery type, DC voltage, charging current, surge rating, protection and warranty in writing.
Do not connect a generator or battery to a house circuit without correctly designed transfer equipment. Back-feeding the grid can put utility workers at risk. Have a qualified installer handle the design and connection.
Use current local rules and model documentation
Grid connection, net metering, subsidies, approved equipment and application steps can change. Check the current Ministry of New and Renewable Energy guidance, your state regulator and DISCOM before committing to a rooftop system.
Our solar and battery tools estimate arithmetic from the values you enter. They do not estimate your local solar yield, guarantee backup, approve grid interconnection or replace an engineering survey.
References
These guides give planning estimates and general safety practices, not engineering advice for a specific installation. Check appliance nameplates and manufacturer documentation, and use a qualified electrician for anything beyond a plug-in appliance.