Nairobi-based off-grid solar company Sun King has secured a $5 million Series D equity investment from Acumen to expand its operations in Zambia and use the capital to unlock additional local-currency debt.

The investment, made through Acumen’s Hardest-to-Reach (H2R) Catalyze initiative, has been injected directly into Sun King’s Zambian subsidiary. It is Acumen’s first country-level equity investment in Sun King.

The financing is designed to help Sun King scale its pay-as-you-go solar business in Zambia while attracting funding from local financial institutions, according to Acumen.

“The investment will accelerate Sun King’s scale in Zambia and close the energy access gap, while also attracting local currency debt from Zambian financial institutions,” said Sandra Halilovic, head of H2R Catalyze at Acumen.

Acumen’s H2R initiative has raised nearly $250 million to expand access to off-grid solar across 17 sub-Saharan African countries. Its H2R Catalyze programme has $60 million available for equity, debt, grants and technical assistance.

Sun King’s expansion into Zambia comes as the company seeks to replicate a financing model it has used in other African markets, where local-currency debt supports the financing of solar home systems purchased by customers through instalment payments.

The company completed a $156 million local-currency securitisation in Kenya in 2025, backed by Kenyan banks and international development finance institutions.

Securitisation allows Sun King to package future customer repayments into financial assets that can be funded by banks and other investors, reducing the company’s reliance on international hard-currency financing.

The $5 million equity investment therefore serves not only as growth capital but also as a foundation for raising substantially more debt in Zambia.

Sun King is entering a market where electricity access remains limited, particularly in rural areas.

Acumen estimates that its support could enable Sun King to reach nearly 5.6 million people in Zambia over the next five years, with as many as 4.5 million people gaining access to electricity for the first time.

The expansion comes alongside Zambia’s broader push to increase solar power generation. The government’s Presidential Solar Initiative has targeted the addition of 1,000MW of solar capacity to the national grid.

Sun King’s business addresses a different part of the market, providing distributed solar systems to households and businesses that are not connected to reliable grid electricity.

The company uses a pay-as-you-go model that allows customers to acquire solar home systems and repay the cost through smaller, recurring payments.

Founded in 2007, Sun King operates across 11 African and Asian markets, providing solar home systems and related financing to households and small businesses.

The company raised $40 million in equity from Lightrock in December 2025 to support the expansion of its decentralised energy business across Africa and Asia.

In 2022, Sun King raised $260 million in a Series D round led by BeyondNetZero, the climate investing platform of General Atlantic, with participation from M&G Investments’ Catalyst team and Arch Emerging Markets Partners.

The company says it has raised $547 million across 20 funding rounds, including nine debt rounds, and has issued $1.3 billion in solar loans to nearly 10 million customers across Africa.

Its expansion into Zambia will now depend on its ability to build a distribution network, acquire and retain customers and secure sufficient local financing to support its PAYG model.

For Acumen, the investment is intended to demonstrate that equity capital can help off-grid solar companies attract larger pools of local-currency debt, allowing them to scale energy access without relying solely on foreign-currency financing.