Many Nigerians know the frustration of estimated electricity bills, which charge for power that may never have arrived. For a small mini-grid, unpaid bills are just as damaging the other way: if customers don't pay, there's no money for maintenance and batteries, and the system fails.
How prepaid metering works
- The customer buys units in advance by bank transfer, USSD, mobile money or a local vendor.
- They receive a token: a 20-digit code, or credit sent straight to the meter.
- The meter counts down as power is used, and the customer can see their balance.
- When credit runs out, the meter switches off until the next top-up.
The STS standard
Most prepaid meters use the Standard Transfer Specification (STS), an international standard (IEC 62055-41) based on secure 20-digit tokens. Because it's a shared standard, meters and vending systems from different manufacturers can work together, and a token can be typed in by hand when there's no mobile signal.
Why it works well for mini-grids
- No bad debt: power is paid for before it's used.
- No estimated bills: customers pay only for what they use, so billing is transparent.
- Budget control: customers top up small amounts when they can, which suits irregular incomes.
- Less theft: "split" meters put the metering unit on the pole, out of reach, with a small display inside the home.
- Remote monitoring: smart meters report use and faults, so problems are spotted early.
Things to get right
- Offline top-ups: rural mobile networks drop out, so customers must still be able to load tokens.
- Local vendors: not everyone uses banking apps, so cash agents in the community matter.
- Approved tariffs and certified meters: prices and meters must follow the regulator's and safety agency's rules.
The takeaway: prepaid metering is fair to customers and keeps the mini-grid funded. That's why every Urim Energy project plan includes it.