As is the case with any energy conversion, certain losses are inevitable. Less energy eventually makes it to the grid if it passes through the CAES system than in a similar system without storage. Some of these losses are mitigated in the approach used by General Compression (using the wind turbine to compress the air directly). In any event, the requirement for additional heating in the expansion process is the most significant disadvantage. By some estimates, 1 kWh worth of natural gas will be needed for every 3 kWh generated from a CAES system. This is particularly problematic if fossil fuels are used for the heat addition. As natural gas prices increase, the economics of CAES, marginal at present, could fail. Again using the wind energy example, one might view a wind farm using CAES as a gas turbine plant with a 3 fold increase in yield over a conventional gas turbine generator. While this is an impressive improvement, it takes some of the ‘renewable’ luster off the wind farm. It is not clear how policies like the production tax credit or renewable portfolio standards will view this technology.