The reservoirs wait for sunset
The 13:00 stack wears a gold band of 1,241 MW. At 21:00 the band is empty, and total generation is higher, 5,819 MW against 5,061 MW. Hydro moves from 872 MW to 2,068 MW. Reservoirs, taken apart from the river, rise from 216 MW to 927 MW, 4.3 times. Nuclear holds 1,176 MW at noon and 1,202 MW in the evening. Its share falls from 23.2% to 20.7%, because the evening stack is larger. Lignite, from 13.2% to 13.3%.
In winter the lens is thin
The same hour in November, December, January and February: the sun holds 8.9% of the stack. Evening still asks for more water, but the midday gold is a sliver. The winter profile shows how seasonal the lens is, not a second grid.
An hour has a recipe
A washing machine run at noon in summer meets an hour in which a quarter of generated current is sunlight. The same machine at 21:00 meets an hour with no sun, held up by hydro. The price of the hour is a different question. This page shows what the stack is made of.
Method and sources
The stack sums domestic generation: nuclear, lignite, hard coal, gas, run-of-river hydro, reservoir hydro, biomass, wind, solar and batteries. Imports, exports and load stay outside the stack. Each local hour is the mean of that hour's quarter-hour observations, on Romania's clock. The summer profile is the median of hours in May, June, July and August 2025; the winter profile, the median of November, December, January and February. Shares are parts of that hour's stack. A household socket still mixes in imports and losses.
- ENTSO-E Transparency Platform, Actual Generation per Production Type, Romanian bidding zone (10YRO-TEL------P), year 2025.
- Energy-Charts, Fraunhofer ISE, public power series for Romania, accessed 20 August 2026.
The figures describe 2025. A sunnier year, a windier year, or a year with different outages moves the stack. A single consumer’s carbon intensity stays outside this reading.