Grunnlast

Grunnlast, or base load, is the minimum level of electricity demand on a power grid over a period, typically 24 hours. It represents the portion of demand that is relatively predictable and stable and that must be met by continuous, reliable generation.

Plants that provide grunnlast have high capacity factors and low marginal costs. They are designed to operate for long periods with minimal ramping and few start-stop cycles, in order to keep overall production costs down and supply steady.

Common technologies for grunnlast include nuclear, coal, and large-scale hydro plants, which can run continuously and deliver a steady output. Geothermal power can also serve as base load in suitable locations. In some markets, natural gas-fired combined-cycle plants contribute to grunnlast, though they are often used for mid-merit or peak generation due to fuel costs and flexibility needs. Intermittent renewables like wind and solar generally do not form grunnlast unless supported by storage or other firm capacity.

In hydro-dominated systems such as Norway, hydropower frequently acts as grunnlast because it can sustain high output while remaining flexible to adjust to demand. Pumped-storage facilities support balancing and grid stability rather than acting as fixed base-load capacity.

With a growing share of intermittent renewables, the notion of grunnlast is evolving. Modern grids emphasize flexibility, energy storage, and demand-side management to meet the base demand reliably, alongside a diverse mix of generation and cross-border interconnections.