About the Carbon Footprint
A solar system's carbon offset is the grid CO₂ it avoids by displacing coal-heavy grid electricity. It is the generation multiplied by India's grid emission factor, and is often expressed in relatable terms — trees planted, cars taken off the road, or tonnes of coal saved.
Formula
CO₂ avoided (kg) = Annual generation (kWh) × Grid emission factor (kg CO₂/kWh)
- Annual generation
- Units the system produces per year (kWh)
- Grid emission factor
- India's grid CO₂ intensity, ≈0.71–0.82 kg CO₂/kWh (CEA)
Trees equivalent ≈ CO₂ avoided (kg) ÷ 22
- 22
- Approx. kg CO₂ absorbed by one mature tree per year
How to calculate it
- 1Estimate annual generation from system size and specific yield.
- 2Multiply by the CEA grid emission factor (~0.72 kg CO₂/kWh) to get CO₂ avoided per year.
- 3Convert to equivalents: divide by ~22 for trees/year, or use ~0.9 kg CO₂/kg for coal saved.
- 4Multiply by 25 years for the lifetime offset.
Worked example
A 5 kW system generating ~7,500 kWh/year avoids about 7,500 × 0.72 ≈ 5.4 tonnes of CO₂ a year — equivalent to roughly 245 trees, and around 135 tonnes over a 25-year life.
What you can calculate
- CO₂ savings
- Tree equivalents
- Carbon credits
- Environmental impact
Standards & references
Frequently asked questions
How much CO₂ does rooftop solar offset?
Each kWh of solar in India displaces roughly 0.7–0.8 kg of grid CO₂. A typical 5 kW home system avoids about 5 tonnes a year; a 100 kW commercial system avoids over 100 tonnes a year.
Does the offset account for manufacturing emissions?
The headline offset counts operational grid CO₂ avoided. Manufacturing does have an embodied footprint, but a solar panel's energy payback time in India is roughly 1–2 years — after that, decades of generation are effectively carbon-free relative to the grid.
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