Good news for prepaid electricity users with solar power in South Africa
Eskom will soon allow rooftop solar power users on its distribution network to register their systems without migrating to a postpaid tariff.
The power utility announced it was testing this system and intended to proceed to immediate rollout once initial implementation requirements were confirmed.
Once enabled, prepaid customers who register on Eskom’s small-scale embedded generation (SSEG) database will also be exempt from registration fees.
“Customers may retain their existing setup or, where required, have a free smart meter installed, and still qualify for the cost waiver for systems of up to 50kW,” Eskom said.
Many electricity users in South Africa prefer using prepaid, as it can make budgeting for electricity more predictable.
It also avoids the potential for bill shock, stemming from inaccurate consumption estimates by municipalities that don’t regularly check meters for actual usage.
In addition to forcing SSEG customers to postpaid, Eskom Direct customers with rooftop solar systems must move to a postpaid time-of-use (ToU) tariff called Homeflex.
Under its other residential tariff plans, including Homepower, consumption is charged at a fixed per-kWh rate.
Under Homeflex, Eskom divides variable energy charges into three categories — off-peak, standard, and peak — corresponding with periods of low, moderate, and high average electricity demand.
The tariff amounts and precise hours also vary between the lower-demand summer months and the higher-demand winter period.
The standard energy charge is similar to the flat rate on no-ToU plans, while the off-peak tariff is lower and the peak tariff is higher.
The structure aims to encourage the use of grid power for charging batteries during periods of low demand and to discourage its use during peak demand.
The approach has become fairly common among utilities worldwide, driven by increased adoption of distributed self-generation due to rapidly declining solar component costs.
It is unclear whether Eskom’s prepaid system for SSEG users will retain a ToU mechanism, which can be implemented with certain smart prepaid meters.
The Organisation Undoing Tax Abuse has argued that SSEG customers should have the freedom to choose between a flat and a ToU tariff.
Issues with prepaid meters and rooftop solar systems
According to the Electrical Contractors Association of South Africa (Ecasa), there is no universal technical prohibition to connect compliant SSEG systems to installations supplied via prepaid meters.
Ecasa national technical advisor Grant Seeman told MyBroadband one potential issue was that many legacy prepaid meters were not designed to accommodate reverse energy flow.
“Where unpermitted feed-in occurs, this may result in meter malfunction, inaccurate billing, protective disconnection, or consumers being incorrectly charged for exported electricity,” he said.
Many meters deliberately cut off a property’s grid supply when an inverter is not drawing power from the grid, even when the meters are set not to export any electricity back to the grid.
Utilities such as the City of Tshwane provide users with a code to reprogram certain meters to prevent cutoffs. The inverter must also be set to pull a small amount of electricity from the grid.
The minimum draw is typically around 20 watts, which consumes about 0.48kWh per day or 14.4kWh per month, even for users whose systems can support all their demand.
Seeman said that modern smart prepaid meters used by certain utilities may incorporate reverse-power detection and anti-tamper mechanisms to prevent unauthorised export into the distribution network.
“Accordingly, the permissibility of SSEG on a prepaid supply is typically determined by the local supply authority’s approved embedded generation framework,” Seeman said.
The framework may include requirements relating to meter type, protection interfaces, formal application approval, and commissioning.
One city that also forces registered SSEG customers to a postpaid billing plan is the City of Johannesburg.
Its approach has been widely condemned, in part because postpaid fixed charges are over four times those on prepaid.
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