FILE - A photovoltaic solar park situated on the outskirts of the coastal town of Lamberts Bay, South Africa on March. 29,  2016.

TEPIC, MEXICO - Giving the poorest people in the world's fast-growing cities access to affordable, clean energy supplies, while wiping out the use of hazardous solid fuels is essential for urban economies to grow on a warming planet, researchers said.

Some half a billion people in urban areas still cook with traditional fuels like wood, said a report from the Washington-based World Resources Institute (WRI). It urged cities to boost access to solar power and other clean energy sources, and make buildings and domestic appliances more efficient.

“You cannot be a modern, prosperous city in the 21st century unless the energy access challenge is addressed,” Michael Westphal from the WRI Ross Center for Sustainable Cities told the Thomson Reuters Foundation.

“Providing energy services for the under-served really will enhance the environment and the economy for the whole city. It's only when everyone in the city has dependable energy that the city will thrive,” said the report co-author.

Rising migration to already polluted cities means they cannot afford to rely on fossil fuel-based systems developed in rich countries, and should concentrate on clean, cheap energy sources that produce less greenhouse gases, said the report.

Up to 97 percent of people in cities in Latin America and East and South Asia had access to electricity in 2012. But in sub-Saharan Africa, the rate was less than 60 percent, with services often inefficient and unreliable, said the WRI report.

Around 95 million of the 131 million people in urban areas who do not have electricity are in sub-Saharan Africa, it added.

In 2010, as many as 550,000 people died prematurely from indoor pollution due to fuels such as wood and coal, underlining why cities should provide better access to electricity and gas, and promote efficient cookstoves, the report said.

Pricing is key when it comes satisfying growing energy demand. Residents of Nairobi’s Kibera slum spend up to 40 percent of their income on fuel, while high connection charges make grid power unaffordable in some cities, said the report.

Sliding solar costs
Slum dwellers are among those worst-affected by poor energy access, the report said. Some governments don't want to provide infrastructure that could legitimize informal settlements, while lack of tenure and illegal electricity tapping are a hurdle for utilities, it noted.

In some regions, over 15 percent of electricity is lost due to inefficiencies or theft, while 20 percent is stolen in India, said the report.

The potential for solar energy in cities is considerable as equipment costs continue to fall, with community-owned systems helping make services available more widely, it said.

A scheme in Bengaluru, India, allows people to sell power back to the grid, while homeowners in Gujarat are leasing roof space to solar power companies, it noted.

Pay-as-you-go schemes in Kenya, meanwhile, enable consumers to pay for solar systems over a year while buying units of electricity as needed.

Better energy supplies are also important to support the millions of tiny businesses people run from home, and improving the energy efficiency of public buildings like schools and hospitals can cut costs and pollution, the report added.