The percentage share of renewable energy sources in the power production in…

Concept. The share of a source in a country’s power sector is that source’s contribution divided by the sector total, expressed as a percentage — but the contribution can be measured on two different bases, and the two give different numbers. The capacity basis compares installed megawatts; the generation basis compares the units of electricity actually produced. Renewables run at much lower capacity utilisation factors than thermal plants, so their capacity share is always the larger of the two. In Indian official and examination usage the headline figure quoted for "renewable energy sources in power production" is the installed-capacity share reported by the Ministry of New and Renewable Energy, and that is the basis this question is asking on.

Application. The paper is from 2013, so the arithmetic is done on the Indian utility power sector as it stood then, on the capacity basis fixed above:

1. Total installed utility power capacity in India as on 31 March 2013 was about 2,23,000 MW.

2. Grid-interactive renewable capacity on the same date was about 27,500 MW — roughly 18,400 MW wind, 3,800 MW small hydro, 3,600 MW biomass and bagasse cogeneration and 1,700 MW solar.

3. Dividing gives 27,500 / 2,23,000 = 0.123, that is about 12 per cent — close to one-eighth of the country’s power capacity. By December 2013 the same ratio had reached about 12.8 per cent.

4. Twelve per cent falls inside the 10-12% band, and no other band offered is within reach of it.

Cross-check. Test the reading and then the rejected values:

• On the generation basis, renewables supplied about 57,400 GWh of the roughly 9,64,500 GWh generated in 2012-13, that is about 6 per cent — and about 17.7 per cent if large hydro is folded in. Neither figure lands inside any band on offer, so the generation reading cannot be what the item is testing; the capacity reading is, and the official key for this paper marks the 10-12% band.

• Under 1% would mean less than about 2,200 MW of renewables; India had passed that with wind power alone by the late 1990s.

• 2-3% works out to roughly 4,500-6,700 MW, which is the scale of India’s nuclear fleet in 2013 (4,780 MW), not of its renewables.

• 22-25% would require roughly 49,000-56,000 MW of renewables; India only reached that level around 2018.

Result. Measured the way India reports it, the renewable share of the country’s power production at the time of this paper was about 12 per cent, that is around 10-12%. Carry the distinction forward: whenever a percentage of this kind is quoted, check whether it is a share of installed capacity or a share of units generated before you use it.