Consumer groups have joined a court fight against South Australia’s main utility over a proposal to slap increased network charges on households with rooftop solar. The consumer groups see it as a crucial line in the sand to stop other utilities from following suit, and slapping more charges on 1.4 million solar households across the country.

South Australia Power Networks earlier this year revealed plans to charge solar households an extra $100 a year for network use, saying they were adding to network costs rather than reducing them. The Australian Energy Regulator rejected the charge but SAPN has since taken the AER to court over the matter.

Consumer groups say they are joining the court action because the tariff is “discriminatory” and “unnecessary”, and will simply accelerate the move to solar and battery storage, and the move off the grid. This, they say, will create more problems for the network and their remaining customers.

“It will also cause long-term reputational damage to SAPN itself and is likely to accelerate the flight of solar and battery consumers from the grid, creating more of a cost burden for legacy grid-reliant consumers,” the Total Environment Centre says. According to the TEC’s Mark Byrne, if SAPN succeeds in introducing the charge, then other network operators around the country could follow. “We consider it likely that if SAPN is successful in its appeal, other networks around Australia will seek to introduce similarly discriminatory tariffs on solar customers, increasing their costs and slowing the introduction of a decentralised and renewable energy-based electricity system,” Byrne said. “Our role in the case will be to clarify that the electricity rules do not allow networks to discriminate against solar owners under any circumstances.” The TEC is acting with Solar Citizens, a solar consumer group with some 90,000 members, with funding from Energy Consumers Australia. Its application to join the court action was approved by the court on Monday. It is one of a number of legal actions and protests over network costs currently taking place in Australia. In NSW, the state-owned network operators are taking the AER to court over its refusal to accept all their spending plans in the next five years. The Public Interest Advisory Council is joined to that court action, arguing that the AER still allowed too much spending, and unnecessary costs will be passed on to consumers. Networks around Australia are also under fire for tariff changes that the solar industry argues will discriminate against solar households. This includes higher fixed charges in many states, including in Queensland where a household consuming just 1MWh of electricity a year will pay an average of 72c/kWh for electricity. That compares to the wholesale price of around 4c/kWh. Critics say the mark-up – through network charges, retail margins and other margins – is simply not justified and not sustainable. The NSW networks are also considering a form of “solar tax”, imposing network charges on exports from rooftop solar back to the grid.

In the SAPN case, the TEC is supporting the AER position, although it says that the AER’s reasons for rejecting the SAPN solar charge in the first place was mistaken.

The AER rejected it on the basis that SAPN could not prove that solar households had a different profile from other customers. The TEC says SAPN should not be allowed to discriminate against any customer, regardless of load profile.

It cites a clause in the National Electricity Rules – Clause 6.18.4(3)(a) – which is intended to prevent discrimination between customers on the basis of micro-generation technology.

“In plain terms, the wording and intent of that clause are to prevent customers being treated differently in respect of the tariffs they are charged just because some have PV systems on their roofs,” the TEC argues.

“It is therefore irrelevant whether solar customers have a sufficiently different load profile to justify discriminating against them by creating a more expensive tariff for the same load profile.

“Our proposition is twofold: (1) if the test for the tariff class differentiation is based on whether a consumer has PV or not, that is unlawful discrimination; (2) if a customer on the “general tariff” who had the same load profile as a customer with PV would be treated more favourably than the customer with PV,then that is unlawful discrimination.

“Further, or in the alternative, even if the Court decides that such discrimination is lawful if PV and non-PV customers are found to have “sufficiently different” load profiles, we would argue that the load profiles of individual PV customers are so distinct that there is no justification for aggregating and averaging the load profiles of all PV and non-PV customers.

It uses this graph – from the APVI – showing the load profiles of 20 solar customers on the Ausgrid network on a particular day, which bear little relationship to SAPN’s graph averaging the daily load profiles of all its solar customers.

SAPN is also introducing “demand” charges that it says could reduce the uptake of rooftop solar by around half in coming years, although it could accelerate the uptake of battery storage, and even electric vehicles.

The TEC – and other groups – say they support the move to demand tariffs, but argues they should be properly structured. They prefer tariffs based on “critical peak use” – meaning tariffs should be structured according to network peaks, rather than individual consumer peaks, which may be at different times.

Solar Citizens national Director Claire O’Rourke said the SAPN move was an attempt by SAPN to “gouge” solar homeowners. “(They) are again trying to push through unfair fees onto the solar community by any means possible,” O’Rourke said.

South Australia has 190,000 solar households and some 570MW of rooftop solar capacity. Last week, the Australian Energy Market Operator said this could rise five-fold over the next two decades, meaning the rooftop solar could meet all the state’s demand on some days within a decade.

By 2034/35, along with large-scale renewables such as wind energy and solar PV, renewables could be providing the equivalent of all the state’s power needs.