With the massive increase in the demand for power of late, we are finding it difficult to meet our night load. Surprisingly, we are meeting our day load without any difficulty since we have ample renewable, mainly solar, generation. This is despite the fact that the daily peak is now in the afternoon and not evenings as was the case earlier. Our solar capacity has touched 157 gigawatts (Gw), whereas the total renewable capacity (including all forms of hydro) is about 331 Gw.
We have not been able to exploit this capacity fully due to a lack of adequate storage, be it batteries or pumped storage. As a result, we are forced to back down solar generation just to ensure coal-based generation does not go below the technical minimum. Reports say that about 2.3 billion units of solar power were lost between May and December 2025 on account of forced curtailment. It may seem to be a small fraction of solar generation but in absolute terms, it is a huge loss as that amount can light up more than a million homes for one year.
It seems the primary reason for failing to meet the night load is that quite a few coal-based stations are on unscheduled outage. There are some who opine that such stations are getting old and failing to meet the need of continuous generation.
According to the Central Electricity Authority’s latest General Review (which has data till 2024), the total coal-based capacity is 217,000 megawatts (Mw), of which around 42,500 Mw is more than 25 years old. This accounts for only about 20%. One has used the 25-year criterion more on account of economics than technicalities. It is well-known that coal stations can run for 40 years or longer if maintained well, including additional capital investment for upgrade. The power purchase agreements (PPAs), however, are for 25 years initially. Given that about 90% of the coal-based capacity is on long-term PPAs, it means they are earning their fixed costs; so, maintenance should not be a problem.
One can go further back to see how many generating stations are over 40 years old. The capacity addition that has taken place from 1976 till 2000 (see graph) shows that barring a little over 10,000 Mw (commissioned during 1976-1985), all other coal-based units are 40 years old or younger. Plants older than 25 years may have issues over ramping up or down as there was no such concept in old plants with renewable generation and its intermittency not in the picture. They were designed accordingly but baseload generation should proceed without difficulty.
From the point of view of ramping to accommodate intermittency of renewables, the size of coal-generating units is important. Some experts say there are several operational advantages if ramping is done through smaller units. But there are exceptions when a large unit is especially designed for flexible operation. India has a diversified fleet of units ranging from 25 Mw to 800 Mw. Also, it’s not the case that the smaller units (less than 100 Mw) are the oldest. We have ample cases of units of size ranging from 30-60 Mw that were installed somewhere around 2015. This is to our advantage as ramping is easier in new units as compared to old.
Going by the data, one isn’t too sure if India’s coal-generating sector can be labelled as vintage. Besides, our diversified fleet of units is helpful. The fact that the night load is not being met could be due to a variety of other reasons, although poor maintenance could be one of them despite earning a fixed charge. Yet another reason could be the fact that coal-based units are just not designed for two-shift operations and lack the capacity to ramp up or down, at least not at the speed required. To this end, there could be some justification in what is being said by a few generators — that continuous ramping is damaging the machines and such operation should stop. Although the government believes that the technical minimum of operation is 40% of the capacity, the generators feel that sub-55% is detrimental.
Where does the solution lie? We have to enhance storage capacity since it is apparent that our desire to enhance renewable generation is in conflict with our grid realities. This can only get worse as we add to our solar capacity without building up storage. It may be pertinent to add that next year could be worse as demand is expected to go up by 7% during the next fiscal with a drop in hydro generation due to poor monsoons this year. Adding to storage, however, has its own challenges — it is reported that 75% of the upcoming projects awarded in 2025 are facing tariffs that are below the economic minimum (JMK Research and IEEFA). This leaves a big question mark on their successful completion.
Disclaimer: The views expressed are the author’s own and do not reflect the official policy or position of Financial Express.