"Falling costs" refers to the decrease in the amount of money required for something. It means that the price or expenses associated with a particular item or process are going down over time. Full definition
The rapidly falling costs of wind and solar power are enabling businesses to translate their renewable electricity commitments into tangible investments. (there100.org)
It finds that falling costs for solar electricity, and to some extent wind power, is continuing to drive deployment. (uncclearn.org)
Feed - in tariffs set by government or parliament have supported rapid expansion of renewable power production, along with falling costs. (cleanenergywire.org)