Big off-grid inverter problem in South Africa

Many South African households with solar power systems may have to replace their inverters to meet the grid code’s requirements to be compliant with electricity distributors’ rules.

MyBroadband was recently contacted by a concerned solar power user in the City of Johannesburg (CoJ), who has recently been following developments around small-scale embedded generation system (SSEG) registrations.

The resident initially installed a 5kW backup-only power system about two years ago, amid the worst load-shedding the country had ever experienced.

In 2024, he upgraded it with solar panels due to intensified local power outages.

“With just over R70,000 spent in total, we were fairly relieved that we will have a reliable source of electricity going forward, as well as some savings on our monthly electricity bill,” he said.

However, after reading about Eskom and municipalities’ SSEG registration campaigns, he learnt that more costs could be on the cards.

He decided to consult a professional service provider for help registering his system to comply with City Power’s rules.

This decision was motivated in part because City Power had provided little guidance on its website or public communication channels on how to register a system.

It also does not feature on the South African Local Government Association (Salga’s) Small Scale Embedded Energy Generation Application Platform, which uses a simplified one-size-fits-all online registration process.

The service provider told the customer that their Must-branded off-grid inverter was not on the list of “approved inverters.”

“When I asked about ‘the list’, and how I can obtain a copy of it, I was told to just download it from the Internet,” he said.

He was provided with a link to the City of Cape Town’s list of approved inverters, which is regularly updated.

“When I asked about the list for Johannesburg, I was told that there isn’t one and that Cape Town’s list is used nationally,” he said.

Cape Town’s inverter approvals

The City of Cape Town was the first of the major metros to publish a list of approved inverters for grid-tied solar and backup systems.

While the city initially allowed off-grid inverters like the customer’s Must model and various brands of Axpert inverters, it changed to hybrid-only effective 1 October 2023.

Only systems with off-grid inverters which had been authorised before that date would be allowed to function in a grid-tied system.

The city made the change after finding that many solar PV systems using non-approved inverters were not correctly wired, posing safety and grid stability risks.

The city does not actually approve any inverters itself, it only adds those which meet the NRS 097-2-1 standard for Grid Interconnection fo Embedded Generation to the list.

These inverters have been submitted for third-party type testing by their manufacturers to show they can operate safely without causing harm to residents and electricity infrastructure workers while maintaining the integrity of the grid.

“This is particularly the case for anti-islanding,” the CoCt explained. “When the network goes down, the inverter disconnects and does not feed electricity onto the grid.”

“The City has reviewed the certification and test reports of the inverters on the list to verify their compliance. Systems using non-approved inverters will not be authorised.”

Many households were fuming after the CoCT made the change, especially since it came amid the worst year of load-shedding on record.

Off-grid inverters are substantially cheaper than hybrid inverters, with pricing currently around R10,000 compared to R15,000 at the entry-level.

That cost difference is in part due to the additional components but also the cost of the testing.

Many residents mistakenly interpreted this as meaning that the metro was blocking people from going off grid, which was not the case.

If a customer did not want to use a hybrid inverter, they could only continue using their off-grid inverter by cutting off their connection to the grid.

Copying Cape Town’s homework — but only up to a point

With Eskom and more municipalities moving to ensure systems comply with NRS 097-2-1, thousands of systems will likely need to swap out off-grid inverters for hybrid models.

In addition, they will have to pay a qualified electrician to perform the installation.

Some distributors may also require sign-off on their system from an electrical engineer registered with the Engineering Council of South Africa, which could add tens of thousands of rand to making the system compliant.

Instead of publishing their own list of approved inverters or informing their customers of NRS 097-2-1 requirements, many distributors simply use Cape Town’s list.

Whereas Cape Town also stopped approving grid-tied systems with unapproved inverters, it at least made an exception for those systems installed up to a certain date.

It is unclear why other metropolitan municipalities’ electricity distributors cannot make the same compromise.

The “after-the-fact” approach by City Power and other distributors could potentially become a major source of frustration, similar to complying with many other unenforceable bylaws.

The significant enforcement resources required to ensure compliance could simply result in wide-scale disobedience.