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Compare the carbon footprint of rooftop solar panels versus grid electricity. See the carbon payback period and annual CO2 savings by country.
Solar panels produce 20–50 g CO2 per kWh over their lifetime (from manufacturing), compared to 130–820 g for grid electricity depending on the country. The carbon payback period — the time it takes for solar panels to offset their manufacturing emissions — is typically 1–4 years, after which they provide 25+ years of near-zero-carbon electricity.
160
kg CO2/year
1,680
kg CO2/year
Solar panels are not zero-carbon — manufacturing them (mining silicon, aluminium frames, glass, and assembly) produces about 1,500–2,000 kg CO2 per typical 5 kW system. Spread over a 25–30 year lifespan producing ~4,000 kWh/year, this works out to about 20–50 g CO2 per kWh — far less than any fossil fuel source.
The carbon payback period is how long it takes for solar panels to 'pay back' their manufacturing emissions through avoided grid electricity. In India (grid: 0.82 kgCO2/kWh), payback is about 1–1.5 years. In the US (0.42), about 2 years. In the UK (0.18), about 3–4 years. Even in clean-grid countries, solar still pays back within the first few years of a 25+ year lifespan.
Adding a home battery (e.g., Tesla Powerwall: ~10 kWh) allows solar energy to be used in the evening rather than exported to the grid. Manufacturing a 10 kWh lithium-ion battery adds approximately 1,000–1,500 kg CO2 to the system's upfront carbon cost — extending the carbon payback period by 6–18 months. However, batteries significantly increase the proportion of solar energy consumed on-site (self-sufficiency), reducing grid dependence and electricity bills. In high-grid-intensity countries like India and Australia, the battery pays its carbon 'debt' back relatively quickly due to every avoided grid kWh saving more CO2.
Solar panel output depends on peak sun hours, which vary from 1,500 kWh/kWp/year in the UK to 1,800 in the US average, 2,200 in Australia, and 1,600 in India (varying significantly by region). A typical 5 kW system produces 6,000–11,000 kWh per year. South-facing roofs at 30–35° pitch are optimal in the northern hemisphere; east-west splits can capture more morning and evening output. Shade from trees, chimneys, or adjacent buildings is the biggest performance killer — shading even 10% of a panel can reduce the whole string's output by up to 30% without optimisers. Modern microinverters and DC optimisers mitigate this significantly.
Covers practical follow-up questions readers often ask
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