Living With Solar Batteries: Three Australian Households Share Their Story

Image: Gizmodo

Since the Tesla Powerwall burst onto the scene less than two years ago, home batteries have never seemed like a smarter or more viable investment for households with solar. Soon enough it wasn't just Tesla - other options quickly began popping up on the market, giving us a vast variety of batteries for all different homes with all different needs.

We set out to speak to three early adopters of battery technology to see what it's like to live with solar batteries and measure how they have impacted their energy use and - most importantly - their power bills.

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Jeff Pollard: The Suburban Tesla Powerwall

The first house we looked at was a fairly average suburban block near Campbelltown in Sydney, belonging to Jeff Pollard. Jeff had installed a small, less than 3kW system of 11 solar panels back in 2010 when the NSW Solar Bonus Scheme was first introduced. They had served him well over the years, but he was all too aware that his panels were going to become next to useless when the Scheme ended in January of this year.

The feed-in tariffs Jeff would be getting from his excess electricity would be slashed from 20c/kWh to around 5c - well below the price they paid for electricity from the grid. "When we got the details that they were cutting the feed-in tariffs, we did some research into what it was going to cost us," Jeff said. "There was no benefit to having those solar panels at the rates we were getting."

The decision to put in a battery was an easy one. "We decided no one was going to get our money for that power," Jeff explained. "Because we were already generating enough for our own electricity needs." They decided on the Tesla Powerwall mostly as a matter of convenience, as the Powerwall's slim form made it ideal for a small suburban block, while most other batteries were too bulky.

Jeff chose the Powerwall because of its compact size. Image supplied.

Going through Natural Solar for the installation, Jeff found out that his original, almost eight year old solar array was just too old to hook up to the new battery. Technically it would have been possible, but the retrofit would have cost more than just installing a new array of panels. So that is exactly what they did.

A new 6kW system was installed in and around the existing panels, with a total of 24 new panels added. The two systems function as separate entities, with the old system feeding directly back into the grid and the new system going into the battery. The installation happened last September with the entire system cost just under $19,000, including the installation of a smart meter. Unfortunately the Pollards missed out on the new and improved Powerwall 2 by just a few months.

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Still, the original 7kWh Powerwall seems to be doing quite well for them, even if it has already been supplanted by its more powerful successor. With four people living in the house, Jeff has calculated a payback period of just four years for the full system - well below average estimates for similar set-ups.

While the family's bills have always been quite cheap thanks to their solar panels - around $200-250 per quarter - the new system has given some amazing results. Jeff has received two bills since the installation in September. The first had him paying only $16 after the feed-in tariffs were paid out, while the second bill, covering the summer period from January through March, was $176 in credit. This is despite March being almost entirely rained out, Jeff was quick to point out. Most of that month averaged a solar production of only 10kWh per day, compared to January when daily production had been as high as 40kWh.

Some of the stats from Jeff's system in January (left) and July (right). Note that Jeff is only able to monitor the solar system connected to the battery, not the separate system exporting to the grid.

As the weather progressed into winter his solar generation dropped and the household's energy use increased, with a number of particularly cold days causing the heater to be run more than usual. "In the summer we were exporting roughly as much as we were importing, now in the winter we're using a bit more and generating a bit less," Jeff said. Daily generation in June was a lot lower than the summer months, dropping down to an average of around 20kWh per day.

Overall, after a number of smart decision the system seems to have been a worthwhile investment for the Pollards. It's not just the battery and the solar panels - the smart meter and SolarEdge's monitoring dashboard help Jeff keep an eye on both input and output. He's also swapped his electricity contract over to Diamond Energy, a renewable-focused retailer with higher feed-in tariffs and even a system where they'll pay up to 32c/kWh to take extra solar energy during peak demand times in the summer.

"The system is working exactly how we planned it to work," Jeff concluded. There were a few minor issues with the installation, he said, but everything was rectified without too much fuss. Now that it's up and going the system pretty much runs itself, bringing the Pollards not just savings but earnings on their electricity bill.


Adrian Shand: The Off-Grid Redflow ZCell

The second battery installation we looked at is a far cry from Jeff's suburban Sydney home. Adrian Shand and his partner live in an old stone cottage in Central Victoria, some ways north of Ballarat. The remote property is entirely disconnected from the grid, meaning Adrian has to generate all the electricity the home uses on site.

For a house like Adrian's, a conventional battery like the Powerwall just isn't going to cut it. As the bulk of his household energy has to be drawn from the battery, he can't risk using one that would provide intermittent or low power as it cycles down. Traditional batteries have no way to prevent this, as by and large they're designed to work in tandem with the grid. This meant Adrian had to look towards the more robust design of a flow battery: the Australian-manufactured Redflow ZCell, to be precise.

As his property has always been off-grid, the ZCell isn't Adrian's first battery. Previously they were using a 1.5kWh lead-acid battery that had come with the house, along with a backup petrol generator. The upgrade in storage capacity has been pretty dramatic, with the old battery being replaced by not one ZCell but two, with a total capacity of 20kWh.

With a 5.2kW array of 21 solar panels, the Shands have much more storage than you'd see on a conventional, grid-connected battery installation. It makes sense - the set up never generates more energy than the batteries can take in, as without a grid connection there's no way to benefit from excess energy.

The installation, which went in around three months ago, cost around $56,000 including solar panels, cables and inverters - the whole package. To most people this figure must sound prohibitively expensive, until you compare it to the cost of getting a house like Adrian's connected to the grid, a project that would cost around $200,000 even without factoring in the bills that come after.

In this case, investing in a robust battery system was the far more cost-effective solution. While the house had existing solar and a battery, Adrian decided to treat everything as a brand new installation, upgrading almost everything from the solar panels to the cabling.

The time finally came to upgrade the system after Adrian found himself in a position to afford the expensive overhaul. He explained that he chose the ZCells over more cost-effective battery options because of their cutting-edge zinc-bromine flow chemistry. "It is 100 per cent based on the chemistry," he said. "Which is far and away better than anything else. The main criteria were stability, and getting the most bang for buck, the most power that we could get for the least money. It wasn't necessarily a per kWh cost, it was more the longevity and lifespan of the battery."

"Further to that was ease of use," Adrian added, bringing up a key point of difference between flow batteries and their conventional cousins. "Lead-acid setups are very hands on, there's a lot of daily maintenance involved and we wanted to get away from that and move into the 'smart battery' idea." It wasn't just Redflow's zinc-bromine batteries they looked at either, Adrian investigated a number of alternatives, including the more well-known lithium-ion batteries, but the ZCell had the most to offer in terms of stability and resistance to long-term degradation.

The two ZCells and battery enclosure on Adrian's property

"Saying that, we are early adopters and we do understand that we've picked up a technology that is in its infancy, but as the chemistry goes the zinc-bromide is just offering much better theoretical output and stability."

While Adrian has no conventional power bills to compare costs from, their reliance on the petrol generator has dramatically decreased. The house is designed to be efficient in its energy use, only using around 5kWh/day, but the difference with the new setup is still dramatic. Previously they would use a full tank of petrol in the generator every three days on average, at a cost of around $25. Now, the generator only needs to be turned on once a fortnight, rarely running through a full tank.

Given that we caught up in the middle of winter, and with Adrian's home being located in one of the lowest areas for solar energy in Australia, the last few weeks have been some of the worst for solar generation - but even then the system has served robustly. Despite Redflow's warning that the ZCell may not function properly if the internal temperature dropped below 15 degrees, Adrian reports that the batteries have run perfectly even through a cold, -2 degree Victorian night.

Adrian's energy consumption during a cold week in late June.

For Adrian this installation has been more than just a way to power his house - it's a proof-of-concept for grand future plans. In the works are a potential 'mini-grid' system that would include not just the house, but a planned editing and mixing studio on the property for Adrian's work as a sound engineer. "These batteries will deliver clean power for when I have people bringing 10,000 amps into the studio," he explained.

While Adrian does have a few qualms with the ZCell, they're fairly minor compared to the benefits - he mainly just doesn't like the way they look. "They're the Excel spreadsheet of batteries," he joked, not a huge fan of Redflow's utilitarian design.

He has one other warning for people looking to install a ZCell at their own home - they do make some noise. He describes it to be like a fridge's hum, but with a more 'gurgling' quality of noise. It's not a problem when the batteries have their own enclosure on the property, but it might cause some issues for people looking to situate the batteries in or close to their homes.

The ZCell's built-in dashboard is more utilitarian

I finished off our chat with a hypothetical - if Adrian was connected to the grid, would he still make the investment in batteries? His answer was an immediate yes. "I can't see why people wouldn't be investigating this seriously," he says, explaining that even his mother had asked him about putting batteries on her suburban block.

For Adrian, however, living off-grid is perfect. "I didn't realise this would be such a big deal for me, but I go to the letterbox and I don't receive any bills," Adrian explained. "There's not this sort of constant demand on your finances. It's a small thing, but it really does make you feel like you're doing things the way you want to do them."


Bjorn Sturnberg: The Student Housing Co-Op With Enphase Batteries

The last installation we looked at wasn't on a house at all, but on a student housing co-op with 40 residents: Newtown's Stucco. The massive project made use of Enphase's scaleable modular AC Battery. It holds the record for being the largest single installation yet for Enphase, and its first project on an apartment block.

The rooftop at Stucco. Image: Gizmodo

The project was the brain-child of former resident Bjorn Sturmberg, who stayed at Stucco for five years while studying for his PhD in solar. As Stucco is run fully as a co-operative, he explains, projects like these are not uncommon. Projects on this scale, however, are almost unheard of.

Bjorn saw the "Stucco Storage and Solar Project" as a "fun little summer project just to finish off my time here," but it soon became so much more than that. While he had tried to put solar panels on the roof a number of times before, it was always just too expensive for the co-op (which caters to low-income students) to afford.

The only reason it finally got off the ground was a sizable City Of Sydney grant allocated for sustainability projects on apartment blocks. Stucco was given the maximum grant of $80,000 - but even that wasn't enough to see the project to completion.

The battery enclosure at Stucco hosts 36 Enphase batteries. Image: Gizmodo

The technical side of the Stucco installation was surprisingly straightforward. Once it got off the ground, all 114 solar panels and 36 Enphase batteries were in place in around three days. The biggest problem the project faced was regulatory, and without hundreds of hours in pro-bono legal support the project would have quickly become unfeasible. To get the system running on an apartment block with many individual residents, Stucco had to get a license to sell electricity - which was relatively easy - and approval to become an embedded network - which was much, much harder.

An embedded network refers to an apartment building where the building owners sell electricity directly to the tenants, rather than letting each tenant choose their own retailer. The Australian Energy Regulator is generally against embedded networks, as they take away the tenants' freedom of choice - even in situations where embedded networks would let them pay less for clean energy generated onsite. It's a tricky issue when you add solar into the mix, and one that is hard to explain succinctly.

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Thankfully, Stucco's physical system works perfectly. The roof hosts a 30.2kW solar system that's linked to 40kWh of useable storage through a system of stacked Enphase batteries. It was an easy system to install at Stucco, with lots of good roof space for solar and an enclosure for the batteries down the bottom of the building, though the latter required a number of fireproofing measures before the batteries could go in.

"The aim was to achieve around 80 per cent self-sufficiency, and so far we've managed around 76 per cent," Bjorn said. "The amount of solar generation is significantly more than total consumption, so the whole building is carbon negative, which is a really satisfying place to be." To be more exact, Stucco is producing 128 per cent of the building's demand.

Of course, even the power they do have to buy from the grid is certified 'green power' through Powershop, so it's all carbon neutral. "But that's just because we're a bunch of do-gooder students," Bjorn explained. When solar generation is factored in, the building's net carbon abatement since the installation has been 11,459kg.

A screenshot from Stucco's monitoring system on a high-yield day in February.

While Stucco only gets a feed-in tariff of 8.2c/kWh, which Bjorn is "very much looking forward to seeing increase eventually," the savings gained by the battery installation make up for it. Since installing the system, Stucco has seen a 90 per cent saving on grid bills. Where before they were buying about $1200 from the grid per month, now it's down to only $110 a month.

Some of those savings go to the residents and some go to the co-op, with Stucco set up as a retailer that sells solar energy on to the tenants. The system is fairly complicated, requiring systems to monitor how much energy tenants use and when. If they happen to be using grid power they'll be charged the same amount as the grid electricity price, while solar power is sold at a discounted rate of around 20-25 per cent. "The incentive remains to shift your behaviour to using [electricity] during the daylight hours, or with the batteries during the early evening," Bjorn said.

A more recent screenshot showing generation and usage in May.

The batteries have usually been enough to take Stucco through a good part of the night: "the power that we are pulling from the grid is predominantly between midnight and when the sun comes up," Bjorn explained, "or at moments when the batteries can't provide enough instantaneous power -- so maybe 90 per cent of the load is met by the batteries, and just a little bit of the peak has to come out of the grid just to support them."

Despite the project's success, Bjorn isn't here to tell people to follow his lead with Stucco's project. In fact, he wouldn't recommend it at all: "This is really hard and not particularly scaleable in the way we did it."

There's a reason there's not much solar on strata, and it's not going to become any easier until new regulations are introduced to specifically cater for solar-powered apartment blocks. Some apartment blocks choose to take the easier route, installing solar to power common areas and hallway lighting, for example, rather than using it in every tenant's apartment.

Still, the Stucco project is a valuable resource for anyone looking to do something similar. "We got this funding to see what could be done, and then to learn a lot, and then to show everyone what we learned," Bjorn said. He has gone on from this project to found his own company that's aimed at putting solar on rental properties - though the new project, SunTenants, focuses on single dwellings instead of whole blocks. Despite all the difficulties, Bjorn's hard work has left a lasting impact on Stucco. "It's still, in the end, the best thing to have done, and if an apartment block has the time and the energy and the resources, they totally should do it."