Efficient lighting would save $110 billion a year worldwide, according to a UN-led study published at the Rio+20 summit on Thursday.

Yearly savings in phasing out incandescent bulbs and making other simple changes would amount to around five percent of global electricity consumption, it said.

It would reduce worldwide output of carbon dioxide (CO2), the main greenhouse gas, by six percent -- the equivalent of more than 450 coal-fired power plants or more than 122 million mid-sized cars, it said.

The report was released by the UN Environment Program (UNEP) and the Global Environment Facility, in conjunction with the International Energy Agency (IEA).

The figures come from an assessment of 150 countries.

Fourteen countries are to be enrolled in a pilot project to develop national plans to phase in fluorescent bulbs or light-emitting diode (LED) lamps.