Baseload was once the cheapest and most reliable way to ensure 24/7 electricity, but falling costs of solar and wind make them the new economic backbone. For much of the 20th century, baseload coal, nuclear, and large hydropower plants were the cheapest way to ensure round-the-clock electricity supply. These plants operated continuously, providing stability and predictability, while more flexible plants handled peaks. However, the cost structure has changed dramatically: in most European markets, solar and wind are now the lowest-cost options for new generation, with near-zero marginal costs and faster deployment times. As these sources are dispatched first, they increasingly displace conventional baseload generation, reducing the utilization and financial viability of coal and nuclear plants.
This trend is visible in Bulgaria as well. Although coal and nuclear still accounted for around 63% of electricity supply in 2024, their share is declining. Solar PV has grown rapidly, covering more than 50% of daytime demand on multiple occasions during 2024–2025. A landmark event occurred on 10 April 2025, when the Electricity System Operator (ESO) reported that solar generation alone provided up to 80% of Bulgaria’s total system demand. This is a clear demonstration that renewables are no longer marginal but central to system operation, even in a country traditionally dependent on baseload.
Source: Klimateka
The Bulgarian case highlights the broader European transition: baseload is no longer the backbone of the system, but rather one of several sources competing for a shrinking share of residual demand. The focus has shifted toward flexibility – storage, interconnections, and demand-side management – which ensures reliability in a system increasingly shaped by variable renewables.