LONDON — Enormous amounts of capital investment — up to $2.5 trillion a year — will be needed to supply the world’s energy needs through 2035, according to a report released Monday by the International Energy Agency, the intergovernmental organization based in Paris.

A total of $40 trillion would go to developing and maintaining energy supplies, with $8 trillion more being spent on energy efficiency, the organization said in the report.

And even that amount of investment would not eliminate many of the issues the industry faces. In fact, they could grow worse over the next two decades, according to the I.E.A., which was established in 1974 to promote energy security after the oil embargo by members of the Organization of the Petroleum Exporting Countries.

The I.E.A. report foresees what could be an erosion of the bargaining power of consumers. For instance, the organization predicts that the surge in supplies of oil and gas from shale rock in North America and elsewhere that have reduced the leverage of oil-producing countries are likely to “run out of steam in the 2020s.”