The young man had always wanted to help people but did not have the stomach to go into medicine, so he opted for engineering. He was only 19 when he invented his first solar lamp after using part of his student loan to buy what he needed.
"Then, I never thought it would take off on this scale. I just wanted to take one to my grandma," he recalled.
Some 15,000 lamps have been turned out since production started in 2004, and Wadongo says his goal is to hit 100,000 by 2015.
"I started in the village where I grew up and I saw kids going from primary into high school," he told AFP.
He has no time for Kenya's political class, accusing them of "wanting people to remain poor so that they can stay in power."
For Wadongo, the lamps are not an end in themselves, but rather "a way to lift people out of poverty."
He and his team from the "Use Solar, Save Lives" project start by identifying impoverished communities that rely for lighting on kerosene lamps -- when they can afford the fuel. They hand out 30 lamps to a community association, often a women's group, and encourage the locality to pool the money each family has saved by no longer buying kerosene.