Off-grid energy services company M-Kopa announced this month it has signed up 100,000 households to its mobile phone-enabled solar service and is adding a further 2,500 a week throughout East Africa.

The pay-as-you-go model, launched in 2010, allows rural customers access to a solar panel product  that taps into cell phone networks for daily or weekly billing cycles, and customer alerts.

M-KOPA operates as a tiny utility, aggregating and building out solar projects, said industry analyst Gigaom.

In April this year the company had 300 employees, it works with another 700 people — independent entrepreneurs and shop owners — who sell its solar products across Kenya and has a 24-hour customer call center staffed by 100 employees.

M-Kopa recently launched a third-generation solar device with two LED solar lights, a solar rechargeable LED torch, a 8W panel (larger than before with 60 percent more charge), a radio, a mobile phone charger and a larger battery.

M-KOPA isn’t the only company using cell phone infrastructure to enable solar across rural areas. D. Light, which makes some of the devices that M-KOPA sells, says it’s reached its 500,000th pay-as-you-go solar customer.

British startup Azuri was planning to hit 75,000 pay-as-you-go solar customers by the end of last year.

M-KOPA was founded in 2010 by the original creators of the mobile payment system M-PESA, which was developed by telecom giant Vodafone.