Coal is "40%", less the energy used in mining and transporting the coal, less the energy used in coping disposing of the ash and coping with the environmental and health harms arising from burning coal.

For PV, a higher "efficiency" means less land is used for a given nameplate power output. Desert land is not in noticeably short supply, though.

Or it might mean that PV is economically feasible in high-latitude or chronically cloudy areas.