Already 30 years ago, in Lower Saxony, a 290 MW CAES power plant was connected to the grid, in order to refine base-load electricity from the Unterweser nuclear power plant, producing peak-load electricity. This power plant has been working as minutes reserve to this day, with high availability, although with relatively low overall efficiency. About 1.6 kWh of gas, and 0.8 kWh of base-load electricity are required in order to generate 1 kWh of peak-load electricity. This is essentially due to the fact that the air which is heated upon compression must be cooled down before it is stored in the cavern. Conversely, the cooling which occurs upon expansion in the turbine must be compensated for by use of natural gas. A power plant in McIntosh, USA, utilises heat from turbine exhaust gases, via a heat exchanger, to preheat the compressed air. Thus, this power plant, which was commissioned in 1991, achieves a somewhat higher efficiency.

In the future, 'adiabatic storage power plants' (AA-CAES) should be able to operate without any fossil fuels, and require about 1.4 kWh of low-load electricity to generate 1 kWh of peak-load electricity.
It is estimated that the investment costs of a conventional CAES power plant will be of a similar scale to those of comparable peak-load power plants. The same applies to the operating costs. Already, with rising fuel prices, it may very soon be profitable for large power companies to convert cheap excess electricity into valuable reserve energy with compressed air storage.