The International Energy Agency (IEA) says there's an urgent need to improve cooling efficiency as energy demand for air conditioners surges around the world, calling this a "critical blind spot" in the global energy debate.

Worldwide energy demand from air conditioners is expected to triple by 2050, requiring new electricity capacity the equivalent to the combined electricity capacity of the United States, the EU and Japan today, according to a new IEA report.

The global stock of air conditioners in buildings will grow to 5.6 billion by 2050, up from 1.6 billion today - which amounts to 10 new ACs sold every second for the next 30 years, according to the IEA.

Using air conditioners and electric fans to stay cool already accounts for about a fifth of the total electricity used in buildings around the world - or 10 percent of all global electricity consumption today. But as incomes and living standards improve in many developing countries, the growth in AC demand in hotter regions is set to soar.

AC use is expected to be the second-largest source of global electricity demand growth after the industry sector, and the strongest driver for buildings by 2050.

Supplying power to these ACs comes with large costs and environmental implications, the IEA says. One crucial factor is that the efficiency of these new ACs can vary widely. For example, ACs sold in Japan and the European Union are typically 25 percent more efficient than those sold in the United States and China. Efficiency improvements could cut the energy growth from AC demand in half through mandatory energy performance standards.

"Growing electricity demand for air conditioning is one of the most critical blind spots in today's energy debate," IEA executive director Fatih Birol, said in a statement.

"With rising incomes, air conditioner ownership will skyrocket, especially in the emerging world. While this will bring extra comfort and improve daily lives, it is essential that efficiency performance for ACs be prioritized. Standards for the bulk of these new ACs are much lower than where they should be."

Through stringent minimum energy performance standards and other measures such as labelling, the IEA says the average energy efficiency of the stock of ACs worldwide could more than double between now and 2050, creating a scenario that is compatible with the goals of the Paris Agreement.

Making cooling more efficient would also yield multiple benefits, the agency says, making it more affordable, more secure, and more sustainable, and saving as much as US$2.9 trillion in investment, fuel and operating costs.