Guided story
When Does India Actually Turn the Power On?
India's electricity demand peaks after dark, while solar generation vanishes. The evening ramp now dictates the grid's hardest hour, and that hour keeps climbing.
When does India actually use the most electricity?
Not when you might think, and not when the sun is blazing. On an average summer day the grid is already working hard by late morning: total demand hovers around 210 GW through the late morning and afternoon. Right about then, solar comes flooding in. At its peak around midday, solar pushes out about 48 GW, covering roughly a fifth of everything the country is drawing. If you strip that solar out and look at what the rest of the system has to supply, the line sags through the middle of the afternoon into a distinct belly, net demand drops to about 161 GW at 1pm.
Then the sun goes down. Solar generationsolar generationThe electricity produced by solar panels at a given moment. It follows the sun, peaking around noon and falling to zero after sunset. It is instantaneous, not cumulative energy.Solar's timing creates the duck curve because it disappears just when evening demand rises. collapses toward zero. People come home, lights and fans and ACs stay on, and demand climbs to its real high for the day around seven in the evening, touching about 202 GW. That is a steep ramp: roughly 40 GW added in about six hours. And from 1pm to 7pm, solar’s share of demand falls from about 22% to essentially nothing. No amount of midday sunshine can cover an evening that arrives after sunset. The shape of that net-demand line, low belly, sharp evening neck, is the duck curveduck curveThe shape of net electricity demand across a day when a lot of solar power is on the grid. It dips low in the middle of the day (the belly) and rises steeply in the evening (the neck), like a duck's profile. It shows how solar reduces midday load but leaves the evening peak untouched.India's grid now shows this shape because solar pushes net demand down at midday, but the real peak arrives after sunset., and it captures the core timing mismatch that now defines India’s grid challenge.
Solar peaks at noon, demand peaks after dark
mendeley:y58jknpgs8:summer2024
On an average summer day, net demand sags to about 161 GW at 1pm but then climbs to roughly 202 GW by 7pm, after solar has vanished—a 40 GW ramp in six hours.
This chart shows three lines for a typical summer day in 2024: total electricity demand met, solar generation, and net demand (demand minus solar). Total demand runs high, around 210 GW through the late morning and afternoon. Solar generation rises from near zero at 6am to a peak of about 48 GW around midday, covering about 22% of total demand at 1pm. Subtract solar and net demand dips to a low of about 161 GW. As the sun goes down, solar output drops toward zero by 6pm. Meanwhile, demand stays elevated into the evening, pushing net demand up sharply to around 202 GW by 7pm. The net demand curve—low belly, steep neck—is the duck curve. It reveals that solar provides huge midday relief but does nothing for the evening peak, leaving a large and fast ramp for the rest of the power fleet to meet.
Does the peak hour change across the year?
The daily shape is not locked to one clock. As seasons turn, the curve shifts. In summer and the monsoon, demand stays high from late morning well into the evening, riding a broad plateau. Winter tells a different story: the night-time trough is much deeper. At midnight, summer demand sits at around 195.5 GW, while winter drops to 151.9 GW. By early morning, winter is the lowest of the three, but it then climbs fast, a sharp shoulder as heaters and lights come on before dawn.
Yet across all seasons, one pattern holds stubbornly: the evening is always a peak. In summer and monsoon, the evening high blends into a long elevated stretch; in winter, it is a pronounced spike after the day’s work. The hour of the absolute high may slide, summer’s peak is often in the afternoon heat, winter’s right after sunset, but the grid never gets a quiet evening. That persistence is why the timing question matters year-round, not just in May.
How the daily peak moves with the season
mendeley:y58jknpgs8:seasonal2024
Winter demand plunges much lower overnight—151.9 GW at midnight versus 195.5 GW in summer—but the evening remains a stubborn peak across all seasons.
This chart plots average demand met for three seasons in 2024: summer (March-May), monsoon (June-September), and winter (October-February). Summer and monsoon demand are high and plateau-like from late morning into the evening, staying above 190 GW for many hours. Winter demand traces a deeper trough in the small hours, dropping to around 145 GW by 3am, and then rises sharply through a morning shoulder to peak in the early evening. Despite these shifts, the early evening—roughly 6pm to 8pm—emerges as a peak point in all three curves. The absolute timing can slide: on some days the record high is in the afternoon, but the early evening consistently sees demand near or at its daily maximum. This seasonal persistence of the evening peak means that the timing mismatch with solar is not just a summer story; it is built into the year-round rhythm.
Why does the exact hour matter more every year?
Because the single hardest hour the grid has to serve keeps climbing. India’s all-India peak demandpeak demandThe highest power draw recorded during a period (a day, a season, or a year). It is a single moment, not an average. The grid must be sized to handle these peaks even if they last only an hour.India's annual peak demand is rising fast, making the grid's evening ramp harder to manage every year. met was about 158.8 GW in 2017. By 2024, it had hit a record 248.7 GW on 30 May at 3pm, a 57% increase in seven years. The 2025 figure, 240.4 GW from a partial year, will almost certainly be surpassed when remaining months are tallied.
Each new record raises the stakes for that evening ramp. When the annual peak was 159 GW, the climb from a midday belly to the evening high was one size. At nearly 250 GW, the same shape demands much more from the generators and wires that must carry that evening surge. The grid can add more solar, sure, but that only deepens the midday belly; it does not touch the seven-o-clock peak. The mismatch between solar’s hours and the hour of highest need grows wider as both total demand and solar capacity increase. That is why the exact hour of peak demand matters at a scale it never did before: the same clock problem becomes more expensive every year.
India's peak demand keeps breaking records
grid-india · peak_gw
2025 · latest point
India's all-India peak demand met rose from 158.8 GW in 2017 to a record 248.7 GW in 2024—a 57% increase in seven years—making the evening ramp harder each year.
This line chart tracks the single highest instantaneous demand met in each year from 2017 to 2025. The climb is steep and steady: 158.8 GW in 2017, 173.9 GW in 2018, 182.4 GW in 2019, 180.9 GW in 2020 (a slight dip during the pandemic year), then resuming upward to 199.7 GW in 2021, 209.9 GW in 2022, 237.4 GW in 2023, and 248.7 GW in 2024—set on 30 May at 3pm. The 2025 point, 240.4 GW from a partial year, is already close and will almost certainly be exceeded. Each new annual peak raises the grid’s requirement for the hour of maximum strain. When that peak falls in the afternoon (as in 2024), it does not erase the evening high—net demand still ramps steeply post-sunset. As the annual record pushes toward 250 GW and beyond, the duck curve’s evening neck demands ever more generation and storage that can respond quickly.
How should you read these numbers?
These curves come from Grid-India, the national and regional load despatch centres under the Ministry of Power. The hourly demand, solar generation, and wind data for 2024 were compiled in a Mendeley Data dataset released under a Creative Commons CC-BY licence; the long-run annual peak series is republished by NITI Aayog’s India Climate & Energy Dashboard (ICED). All figures are all-India aggregates and are reported as gigawatts (GW).
A few honest boundaries. The hourly numbers measure “demand met”, electricity actually supplied. If any demand went unserved because of load shedding or grid constraints, that is not in these figures, so they represent a floor on true demand. The daily shape you see for a season is a “typical daytypical dayAn average day constructed by taking the mean of all days in a season. No single date looks exactly like this smooth curve, but it represents the general underlying pattern.The duck curve and seasonal shapes are typical days, smoothing out extremes to reveal the underlying rhythm.,” an average over all the days in that season; no single real date will match the smooth curve exactly. The “demand net of solar” line is simply total demand minus solar generation at each hour. It is the load left for hydro, wind, gas, nuclear, and coal together, not the output of any one fuel. And because these are national totals, they smooth over very different regional grids: states with heavy solar penetration, like those in the west and south, can show a much deeper duck curve than the all-India average implies.
Plain English concepts
duck curve
The shape of net electricity demand across a day when a lot of solar power is on the grid. It dips low in the middle of the day (the belly) and rises steeply in the evening (the neck), like a duck's profile. It shows how solar reduces midday load but leaves the evening peak untouched.
India's grid now shows this shape because solar pushes net demand down at midday, but the real peak arrives after sunset.
net demand
Total electricity demand minus the power generated by solar at that moment. It is the load that all other power sources—coal, gas, hydro, wind, nuclear—together must supply. It does not represent any single fuel's output.
The duck curve is about net demand, not total demand. It reveals the timing problem left for non-solar generators.
GW (gigawatt)
A unit of power equal to one billion watts. Think of it as the rate of electricity use; 1 GW can power roughly 700,000 typical Indian homes at once.
All demand and generation numbers are in GW, making it easy to compare across the day and across years.
demand met
The amount of electricity that was actually supplied to the grid. It does not include demand that went unserved due to outages or load shedding, so it is a minimum estimate of true demand.
Our data is demand met, so it is a floor on true demand. The actual peak demand could be higher if the grid had no constraints.
typical day
An average day constructed by taking the mean of all days in a season. No single date looks exactly like this smooth curve, but it represents the general underlying pattern.
The duck curve and seasonal shapes are typical days, smoothing out extremes to reveal the underlying rhythm.
load curve
A graph that shows how electric power demand changes over time, usually a day or a year. It traces the 'load' the grid must carry hour by hour.
All our charts are load curves, showing demand or net demand across hours or years.
solar generation
The electricity produced by solar panels at a given moment. It follows the sun, peaking around noon and falling to zero after sunset. It is instantaneous, not cumulative energy.
Solar's timing creates the duck curve because it disappears just when evening demand rises.
peak demand
The highest power draw recorded during a period (a day, a season, or a year). It is a single moment, not an average. The grid must be sized to handle these peaks even if they last only an hour.
India's annual peak demand is rising fast, making the grid's evening ramp harder to manage every year.
all-India aggregate
A number that sums or averages across the entire national grid. It can hide differences between regions, like a solar-heavy state versus a coal-heavy one.
The duck curve is an all-India average; some states see a much deeper belly, others barely see it.