But in large parts of emerging markets, solar power does not compete with mains electricity, because there is no grid.

In Bangladesh, where more than two out of three households cannot get electricity out of a socket, some 80,000 homes now own a basic solar panel that generates about 50 watts of power.

The energy is stored in a small battery and can light up three bright, energy-saving lamps for four hours, Sazzad Hossain, manager of Rahimafrooz told a solar industry conference in this southern German town at the end of last week.

"When we started in the early 1990s the villagers didn't believe the module would produce light from the sun. We connected it to a light and when the light went on, people believed, so that's the way we did promotion," he said.

A YEAR'S INCOME FOR A SOLAR PANEL?

A major obstacle to the popularity of solar power was that Bangladesh, with a population of 146 million, has a per capita income of US$440, according to Unicef, while the solar systems offered by Rahimafrooz cost US$300, including a US$30 subsidy.

Only through microcredits backed by the World Bank are citizens able to afford this huge upfront investment.

The loan repayment of US$9 per month is close to the cost of kerosene consumption and is often shared with neighbours who buy some of the electricity. After several years, if the loan is repaid, the panel with a 20-30 year lifespan is their own.

In Laos, for-profit company Sunlabob rents out basic solar modules for households and more advanced systems for village halls, schools and health posts where staff can now cool the vaccines and work through the dark. They also power water pumps.

"The majority of rural households can afford solar lighting. They have no idea how much they spend on candles and kerosene," said Andy Schroeter, managing director of Sunlabob.

Researchers from the German Fraunhofer's Institute for Solar Energy's (ISE) rural electrification South East Asia programme agree that even in the world's poorest regions citizens can afford to pay for basic energy needs.