Chepnyaliliet School, with its rough concrete walls and tin roof, at the end of a dusty lane lined with cacti and wild roses, seems a sleepy place to go looking for early adopters of technology. But that is exactly what Rhoda Sigei is.

The determined nursery teacher was the first person in Bomet county, a verdant patch of Kenya's Great Rift valley, to buy into the potential of solar lamps.

When the headmaster brought some samples to the school, Sigei knew she had to have one so she asked for an advance on her tiny salary. "It was a struggle to get the first one but I didn't stop there. I bought three," she says.

She quickly realised the $8 orange plastic lamps, branded as d.lights, would pay for themselves because she and her husband, who farms a small plot, would no longer have to pay $13 a month in fuel for their paraffin lamp.

That is a substantial saving when you earn just 3 000 Kenyan shillings ($34.50) a month. A reliable light in the evenings would allow Sigei to help her 12-year-old daughter, who is struggling at school, and let her 14-year-old son indulge his interest in science.

It has also allowed Sigei to study for a diploma that could see her promoted to a full teaching job and her earnings trebled.

The d.lights are part of a range of durable and affordable solar lamps made by Sunny Money, a subsidiary of the British charity Solar Aid. By investing in Sunny Money, Solar Aid has enabled the firm to spread to more remote areas such as Bomet, where other shareholder-led ventures might fear to tread.

The fact that they have a philanthropic rather than a purely commercial investor interest affords them extra time to get new markets up and running.

Chepnyaliliet, an hour's drive over rutted tracks from the nearest tarred road, is dark after nightfall, like much of Kenya. The single power line that has run since 2011 to Sigei's school is not connected to any of the nearby homes.

Fewer than 20% of homes in East Africa's largest economy have access to electricity and there is nothing to suggest that hamlets like this, where many of Kenya's 43-million people live, will be connected to the national grid soon.

Sunny Money works by approaching schools and persuading head teachers such as Chepnyaliliet's Richard Bii that their products can transform their pupils' performance.

Milton Cheriot is a prime example. The scruffy 13-year-old spends his spare time falling out of trees, testified to by the scars on his smiling face. His name is stitched into his jersey so his mother can make sure her six children put on the right clothes. Now that he consistently has light in the evening, Milton can concentrate on his homework. "In the old days, we would have a lamp maybe three days a week. Now it's every day. And it doesn't produce smoke."

Eye strain
Nights spent straining your eyes in the light of a flickering paraffin flame often led to headaches, itchy eyes and allergies, he says. He now reads for three hours every evening. It has paid off – he scored 86 out of 100 in general science, a mark that propelled him into second spot in his school's rankings.

"As soon as people saw someone they knew having one of these then everyone wanted to have one," says Bii. Mr B, as everyone calls him, estimates that, after one year of sales, nearly half of the 517 pupils at his school now have the lights at home.