How it's calculated
The system efficiency (default 78%) accounts for inverter losses (~3%), DC-AC conversion (~3%), wiring (~2%), soiling (~5%), and temperature de-rating (~5–10%) combined — broadly the difference between nameplate and real-world output.
Reference sun hours by region
| Region | Sun hours / day |
|---|---|
| Rajasthan, Gujarat (India) | 5.5 – 6.5 |
| Most of India (annual avg) | 4.5 – 5.5 |
| UK, North Europe | 2.5 – 3.5 |
| US Southwest (AZ, NV) | 5.5 – 6.5 |
| US Midwest / Northeast | 3.5 – 4.5 |
| Australia (interior) | 5.5 – 6.5 |
FAQ
How do I find my daily kWh use?
Take your monthly electricity bill in units (kWh) and divide by 30. A 4 BHK Indian home typically uses 12–25 kWh/day; a 2 BHK runs 6–12 kWh/day.
Should I size for 100% of my consumption?
For grid-tied systems with net metering, yes — size to your annual consumption. For off-grid (with batteries), size to 110–130% to handle cloudy days. For grid-tied without net metering, size to your daytime-only load to avoid wasted generation.
What about subsidies?
India offers a central subsidy under PM Surya Ghar Yojana (up to ₹78,000 for 3 kW residential) and additional state-level rebates. Quoted costs above are pre-subsidy installed price — deduct subsidies after.