What size solar system do I need?
Work out the right size from your bill.
How to assess the solar capacity you need
Understand kW versus kWh
kW describes power capacity, while kWh measures energy. One billed electricity unit is normally 1 kWh. Panel ratings describe output under standard test conditions, not a promise that the same power is produced every hour. Energy estimates must account for sunlight, shading, temperature and system losses. The panel capacity alone cannot establish monthly production or bill savings.
Build an annual consumption picture
List monthly units from your bills and calculate annual consumption. A rupee total changes with tariffs and fixed charges, so it is a weaker sizing input. Air conditioners, heaters and pumps can create seasonal differences. Day-versus-night use matters too. Include planned electric vehicles or appliances, but evaluate the economic usefulness of extra capacity rather than automatically buying the largest system the roof can hold.
Use a site-specific yield estimate
A preliminary capacity estimate can divide the desired annual solar energy by the site’s estimated annual kWh yield per installed kW. That requires a roof assessment and appropriate generation model. A blanket rule such as 120 monthly units per kW is not dependable for every roof. Do not use the sunniest month as though it represents the whole year.
Check roof and connection constraints
Usable area must allow for water tanks, shade, walkways and safe cleaning access. Area per kW changes with module dimensions and mounting layout. An engineer should assess structural condition and cable routes. Sanctioned load, consumer category and utility approval limits can also constrain capacity. Do not make a purchase decision from terrace dimensions alone.
Size backup separately from the solar array
Backup requires separate calculations for essential loads, duration, usable battery energy and inverter starting capacity. A large solar array without compatible storage does not solve outages. Request separate estimates for generation, bill savings, backup, total price and assistance. Discuss uncertain assumptions and obtain a written design rather than treating a calculator result as a final engineering recommendation.