The 90% cost reduction claim disturbs me because I find it quite ambiguous. The original quote in the article is: >it reduced the cost of the grid service that

The 90% cost reduction claim disturbs me because I find it quite ambiguous. The original quote in the article is: >it reduced the cost of the grid service that it performs by 90% Let's examine "the grid service that it performs". What does this mean? Which "grid service" is it performing? I imagine the "grid service" it performs is that of inputting energy: it's a source of electricity into the grid. So the claim can be re-written as: >[the battery] reduced the cost of <putting energy into the grid> by 90% Reduced, compared to what, a coal-powered steam turbine power station?