Installers are hyped about a busy market for storage but the new Australian Standard which limits connection to the grid may slow things down, writes Jeremy Chunn, if the networks feel like flexing their muscle.


Australians are getting a buzz about batteries. It’s happening slowly, for sure, but it is happening. For installers and retailers there is the hope that orders will start flowing. For forward-thinking consumers who have the funds there is the thrill of saving solar energy for use after sunset – and paying lower electricity bills.

It’s still early days, and things can go wrong. Plenty are still cautious about some of the chemistries, for a start, but barring a spate of catastrophic fires the industry is pretty confident storage will only become more popular as prices keep falling.

That’s until Australian Standard AS4777.1 came along, which limits exports from inverters to 5kVa. That might not trouble your typical solar household which is exporting much of its solar when no-one’s at home on sunny days, but what does it mean for households with storage – or for those planning battery retrofits?

To some networks, the standard has been interpreted as a 5kVa export limit on systems. But others see it differently, says Clean Energy Council director smart energy Darren Gladman. He gives an example of a household running a 5kW inverter for the solar system and 5kW inverter for a battery system, which sums to 10kW, thereby exceeding the 5kVa limit. “Five plus five equals ten, but we’re only going to allow five, so you fail,” he says. Sure, it would be a spurious interpretation of the standard, he says, but sometimes the rules aren’t fair.

“If you took the hardest line interpretation, which some are indicating they will, which is to add the two inverter capacities, then it will be a limitation to the addition of batteries, and really not a very sensible rule,” he says.

“If anything, having that battery system is more likely to reduce the impact that the network sees.”

Gladman cites Queensland networks Ergon Energy and Energex as taking the right approach, where exports are capped at 5kVa but systems of up to 10kW are allowed. “It’s probably the best interpretation we’ve seen so far,” he says. After all, if you’re requiring an export limitation on the overall system why should you care how much is behind the meter?

By late April not all the distributors had finalised their interpretation of the standard but the CEC had been informed of requests for battery retrofits being knocked back on the grounds they would take capacity over the 5kW limit. “Really, we don’t think that makes a lot of sense,” Gladman says.

Close to the limit

Ergon Energy senior network strategy and policy engineer Don McPhail says the Queensland distributor originally took the same view as the majority of other networks that limiting exports to 5kVa for single-phase systems was the answer. “There were good reasons for that from a voltage balancing and management perspective,” he says. For networks, a priority is to manage voltage, he says, and voltage levels are triggered by exports.

After it paused for a moment to consider its solar-loving customer base, however, Ergon took the view that it didn’t want to stand in the way of the busy battery retrofit market. “We asked ourselves: How can we enable them to be connected and still address our network management concerns,” McPhail says. By capping exports at 5kVa but allowing systems up to 10kVa to connect, McPhail says systems that include large AC-coupled storage capacity will be left undisturbed but the network stability issue will be addressed.

It was a bit of a turnaround for the network. Selectronic senior business development manager Craig Hunter cites the backlash that followed Ergon’s ruling last year that inverters could export no more than 5kVa as reason enough to feel confident the networks will not take a draconian stance.

SA Power Networks has adapted its connection standard application process to make a 5kVa limit the easy online default option, Hunter says, but it allows customers to export more than that from inverters so long as they are prepared to put up with a slightly more involved application process.

“I don’t think it [the connection standard] is going to be as big a drama as everybody thinks it’s going to be,” Hunter says. “If a utility has issues with parts of its network, it gives them the ability to restrict it.”

A different approach

For some networks, the idea of taking a stingy view on how much energy customers can export would only be akin to shooting themselves in the foot. Hunter uses Powercor as an example. “Any restriction they put in place for the likes of any solar installer is also going to restrict their trade they’re doing on their retail solar arm,” he says.

Weak networks may be the ones, he says, that will impose the standards by the letter in order to do what they can to control stability. Western Australia is an example, where restrictions so far have been along the lines of agreeing to requests for larger PV systems and battery storage on the condition that network electricity supply to those customers is limited. “The reason being that if you have 5kW of PV and a 5kW load, and a cloud comes over, the grid then has to support that 5kW of load,” he says. “What their concerns are [in WA] is that, now you’ve got a 5kW battery on there as well and let’s just say for argument’s sake there’s a 10kW load, with 5kW of PV supplying the load along with 5kW coming from the battery … then the battery depletes, a cloud comes over and they now have to supply 10kW of load to the house.”

They call it “flicker”, Hunter says, and it’s the main concern for utilities with weak networks. Most of the east coast NEM is fairly robust, he says.

When he spoke to EcoGeneration Hunter was part of the way through contacting the various networks around the country, but so far his impression is that any planned changes will not be substantial enough to dampen demand for storage. “I know they can do what they like – it’s their network – but I’m sure they’ll think about it properly before they make any drastic changes.”

The 5kW limit is nothing new, says Enphase managing director Asia-Pacific Nathan Dunn. “It’s been an unofficial standard applied by the majority of the DNSPs [distributed network service providers] across the country.” Depending on where in a network an application is made the DNSP will determine whether it is appropriate.

It’s seldom a problem for Enphase as its 1.2kWh batteries can be scaled up or down to suit pretty much any system size, but Dunn says some competitors with very large storage systems will have to ask for permission on nearly every installation. And even if an installer thinks an application will go through without any trouble there can always be hurdles, he says. “It’s about figuring out who you’re working with and whether they have a relaxed approach or more of a rigorous approach.”

Don’t be spooked

For solar households in networks that decide to take a tough stance, there may be a way around any tightening of rules.

SunWiz managing director Warwick Johnston says a system owner who’s going to upgrade beyond 5kW may need to install a three-phase connection. In that case the existing PV system could be left it as is, unchanged regardless of updates in standards. “But how do you achieve that but get some reasonable phase balancing given you have to split the rest of the installation over the remaining two phases?” he says. “It gets complex. It will be interesting to see what plays out there.”

The changes may spook some consumers who are contemplating an investment in storage but Johnston sees a sunny side, agreeing it’s just as likely installers will see an increase in inquiries about energy management systems. Although it may not be straight-forward. “Export-limiting functionality would be available in some [energy management systems],” Johnston says. “But is that functionality approved or how is it viewed by the network distribution operators? It adds complexity.”

He expects there will be plenty of discussion about solutions taking place between the networks and manufacturers, with the solar retailers taking keen interest.

Use your smarts

When it comes to meeting demand for electricity it pays to be flexible. Solar-and-storage systems that include smart energy management software will export to the grid at times when prices – and demand for electricity – are high. Distributors on those occasions will want to buy as much as they can from solar households to on-sell somewhere down the line, taking advantage of any price differential.

“Some of those [energy management] systems are set up to export at times when the grid really needs it, when the price is right,” says Gladman at the CEC.

Limiting the amount of electricity that can be supplied into the network at times of high demand doesn’t make much economic sense, unless you can generate it yourself more cheaply than you can buy it to on-sell.

Most of the time a residential battery will have a neutral or subtractive influence on exports, Gladman says, and when it does boost the amount of energy sold into the grid it’s at a time when the grid is crying out for it.

“It feels like the distribution grid connection rules have still got a long way to go, and as soon as we update them the technology moves on and they start looking out of date again,” Gladman says, making the point that he suspects no malicious intention by the networks but that interpretations of standards are sometimes “ill-informed”, simple as that.