The basic unit of analysis in think tanks and media is nameplate capacity, ie a MW of four-hour battery would be compared to a MW of gas turbines.

The most important driver of power system costs is "firm capacity"; a MW of four-hour battery might be 10%-50% as valuable as a MW of gas turbines given that the latter will run for 100-1000 hours per year when the batteries are empty and the prices are much higher. This is true on the grid or behind the meter.