The leaders of more than half of Africa’s nations gathered this week in Dar es Salaam, Tanzania’s sprawling seaside metropolis, to commit to the biggest burst of spending on electric-power generation in Africa’s history.

The World Bank, African Development Bank and others are pledging at least $35 billion to expand electricity across a continent where more than a half-billion people still don’t have it. About half of the money will go toward solar “minigrids” that serve individual communities. The loans will come at below-market interest rates, a crucial stipulation as global lenders usually charge much higher rates in Africa, citing higher risks.

In an interview, Ajay Banga, the president of the World Bank, cast the initiative in sweeping terms where economic development met societal stability and basic human rights. “Without electricity, we can’t get jobs, health care, skills,” he said. The success of electrification, he said, is “foundational to everything.”

The summit’s promise is to get half of Africa’s 600 million unelectrified people powered up in just six years. That averages out to five million people a month. Mr. Banga said the World Bank, on its own, had not yet even passed the one-million-a-month mark.

Despite the unusually strong statements of political will, many people, particularly in Africa’s beleaguered power sector, expressed deep skepticism. In fact, some noted that one need not look farther than the host country, Tanzania, to find a cautionary tale.