Why Cape Town is banning off-grid inverters for solar installations

The City of Cape Town will stop approving off-grid inverters for use in solar backup systems to curb faulty and dangerous installations of these inverters in households that remain connected to the grid.

Due to the increase in load-shedding, the city has seen a massive surge in applications for grid-tied solar and backup systems, with an average of over 1,000 per month in 2023 compared to 100-200 a year ago.

From 1 October 2023, Cape Town will require that new applications for solar PV and battery systems connected to a building’s wiring use a city-approved inverter and obtain professional clearance.

It will also refuse applications for standby and off-grid systems.

The city explained that considering all systems as grid-tied would dramatically improve authorisation turnaround time, improve safety, and prevent the risk of area outages due to inferior systems connected to the grid by fly-by-night operators.

“Currently, many systems using non-approved inverters are not wired correctly, posing risks to the safety and integrity of the network,” the city said.

“This significantly slows down the registration process because there are too many different wiring configurations for the city professionals to consider. Reducing the wiring configurations speeds up the process.”

The new rules will not apply to mobile solutions like trolley inverters or power stations that can be plugged into wall sockets.

It will also not apply to scenarios where residents completely sever their homes from the grid.

The city’s regulations apply only where there is a connection to the electricity network.

A completely off-grid house with own electricity and water supply

Several upset residents contacted MyBroadband about the issue, pointing out that the hybrid inverters on the city’s approved list were substantially more expensive than off-grid models.

Popular off-grid units typically come white-labelled from brands like Axpert, Growatt, Kodak, and Mecer, and can start at less than R10,000 with a capacity of 5kW.

Hybrid inverters with the same capacity are typically priced between R20,000 to R30,000.

The most affordable hybrid inverter listed on Solar Advice’s website is the LuxPowerTek 5kW unit, which costs R20,125.

The same manufacturer’s off-grid inverter costs R11,902.50 from the same retailer.

An off-grid inverter can also be connected to the grid but is not designed for this purpose.

Whereas a hybrid inverter can use a mix of solar and grid electricity, an off-grid inverter can only use one source at a time.

If your solar capacity becomes insufficient, an off-grid inverter will automatically switch to grid-only power.

However, during a small-scale energy generator (SSEG) installer event held by the city, it became clear that some installers were connecting cheaper off-grid inverters incorrectly.

The city told attendees it had received 120 applications from just one installer who claimed their setups were off-grid but were found to be grid-tied upon inspection.

“Practical experience shows us that standby SSEG systems are often not configured correctly,” the city said.

“Standby inverters are not NRS 097-2-1 approved and must be isolated from the grid via an interlocked changeover switch.”

It also discovered instances where “off-grid” systems had their meters running backwards, meaning consumed electricity was reflected as being fed into the grid.

That would result in households and businesses getting paid for electricity they had consumed.

The city said the guilty installers had refused to comply with its regulations, claiming that the systems were only for standby.

There had been little to no repercussions from the Department of Labour for poor electrical installations either, while fire damage due to poor workmanship and non-compliant components had increased six-fold in a few years.

AWPower managing director Christiaan Hattingh told MyBroadband that the rules about solar installations in Cape Town had always been clear.

“If you wanted to go the solar route, your inverter needed to be on the City of Cape Town’s Approved Inverters List,” Hattingh said.

He explained these inverters were tested according to the NRS 097-2-1 standard.

Regarding SSEG, the specification sets out the technical requirements for the utility interface, the embedded generator and system, and the utility distribution network with respect to embedded generation.

Impact on grid-tied homes planning to get solar

Hattingh said when the new rules come into effect, households with off-grid inverters won’t be allowed to install solar if they are connected to the grid.

In addition to the requirement that all inverters be on the city’s approved list and no off-grid inverters would be allowed, the city is also building an online SSEG application system.

Aside from the safety and approval benefits, using a hybrid inverter will allow customers to get paid for electricity they feed back into the grid at R1.13 per kWh until June 2025.

Lastly, the city is also aware that the cost of Advanced Metering Infrastructure (AMI) meters was a major barrier for residential customers wanting to install grid-tied systems.

It has issued a new tender that includes the provision of single-phase AMIs at a “significantly” reduced price, although the pricing for this remains to be confirmed.

The Residential AMI Access Fee of R96.20 per month is also being replaced by a new residential AMI Administration Fee of R5.66.

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Why Cape Town is banning off-grid inverters for solar installations