Traditional fossil-fuel plants operate at a pre-mitigated level, they provide a consistent and predictable amount of electricity. Renewables, on the other hand, are a much more unreliable source. For example, energy output from a solar farm can drop without warning due to clouds obscuring sunlight from the panels. Similarly, wind speeds cannot be reliably forecasted. To prepare for this fluctuation in advance, research and investment into energy storage systems are on the rise.