We ask five experts: Will battery storage change the way we live?

In the first of a series from SolarQuotes, we ask five eminent experts in the clean energy field to discuss four questions on a selected topic. This month we’ve selected “battery storage” as the launching pad for some fascinating discussion and advice.

Solar and battery storage has been one of the clean energy talking points of 2015 following the dramatic unveiling of the Powerwall by Tesla’s Elon Musk. However as we’ve seen, the Powerwall isn’t the only option out there in the marketplace and the best battery storage option will differ depending on your situation whether on-grid, off-grid or hybrid solar.

With this in mind we’ve asked our experts what these solar battery storage breakthroughs mean for Australian households and small businesses and what the future holds for energy independence.

Our Big Five panel of experts are:

muriel wattMuriel Watt – Head, Energy Policy & PV, IT Power Australia; and Senior Lecturer, School of Photovoltaics and Renewable Energy Engineering, University of NSW, Muriel has worked in government energy agencies, private companies and universities on energy related matters since 1980, with a strong focus on renewable energy research, development, technologies, deployment and policies.


Xantor WeinbergXantor Weinberg – Owner and director of Energo, Xantor is a pioneer of the solar industry and one of the most experienced and highly qualified designers and installers in Australia. Xantor has worked as head installer for larger government systems and schools contracts in NSW and also specialises in off grid and ground mounted system design.


warwickWarwick Johnston – Founder of solar consultancy company SunWiz, Warwick is at the centre of helping solar businesses operate more effectively and efficiency. Sunwiz provides clean energy intelligence and looks to help solar businesses grow sustainably.


Luke OsborneLuke Osborne – Chief Operating Officer Reposit Power. Luke has had vast experience working in the Australian, Canadian, USA, NZ and South African electricity sectors. He has been an executive in the electricity industry for over a decade and was formerly COO in Australia’s most successful renewable energy company.


Geoff BraggGeoff Bragg – As Chairman of NSW Solar Energy Industries Assoc (SEIA), Secretary of the Australian Solar Council (ASC) and Secretary of the Australian Energy Storage Council (ESC), Geoff is one of the most qualified and experienced solar operators in the sector. As part of the team at New England Solar Power, he provides technical and practical knowledge for a range of solar systems both on and off grid.


Question #1 What do you say to Australians who ask “what’s the best battery storage for us”?


Warwick Johnston: “If you are connected to the grid and are looking to increase the utilisation of your solar energy, then lithium batteries are best, and you needn’t get a whopping big battery – the first few kWh of storage does the heavy lifting. If you’re not connected to the grid, then lead-acid batteries are the best bang for [your] buck.”

Xantor Weinberg: “I would suggest three things at present:

  1. If you want to use a battery with predictable outcome, use lead/acid or lead/gel.
  2. If you want to use a potentially much better and – per kWh storage over its lifetime – cheaper battery, use lithium.
  3. If you don’t want to spend the money right now and want to wait for the lithium prices to come down, use AGM batteries.

These will last you 3 to 5 years and bridge the time until lithium batteries are a not such a big investment. I try to make it as simple as possible for the customers, so I ask them some questions and come up with a suggestion [based on their answers].

Muriel Watt: “This depends what they want to use storage for – to prevent export of PV electricity, to provide back-up during blackouts, to reduce demand during peak tariff periods, to reduce peak demand charges etc.  

For households with PV and who want to make sure they can use all the power they produce, lead-acid batteries are the best choice for now, because their performance is well established and installation standards are in place.  Li-ion batteries look promising, but we need to know more about the performance of the different types, under different conditions of use.  We also need to develop safety standards for use in houses.  Householders should check with their insurance companies before installing Li-ion batteries in their homes.”

Luke Osborne: “The best storage is one that complements your home, your solar (if you already have it) and your consumption patterns.

There are several things to think about, starting with the space available. There are indoor-rated units and outdoor-rated units. Then of course there is the energy storage capacity, measured in kWh and the power, measured in kW. The GridCredits controller will use a system with more energy capacity to increase the self consumption ratio – meaning you consume more of the energy that is generated by your solar. If the unit is too small, it will fill up and you will lose solar to the grid. A high power unit will be able to keep up with large solar systems and/or heavy instantaneous consumption.

A high power system will also be able to earn more with Reposit’s GridCredits system, which sells energy back into the grid when there are price spikes. The more energy you can push out during the price spikes, the more you can earn.”

Geoff Bragg: “I’d say that depends on what you are trying to achieve. There are some critical questions that could be asked:

  • Does the existing solar PV system generate enough energy to meet the average daily consumption of energy?
  • What proportion of energy consumption occurs at night?
  • If net metered, how much energy is currently exporting to the grid?
  • Is back-up power during grid outages valued?
  • How much autonomy is required? Are you comfortable being reliant on grid power, or do you want the grid only as a backup?
  • Are you looking to expand later, and perhaps leave the grid down the track?
  • Is payback period or a high level of autonomy more important?

The answers to these questions will help decide how much energy storage is required, as well as the inverter/charger/energy management system that is most appropriate.There are a growing number of manufacturers and design architectures, and each have their pros and cons.

One notable and atypical feature of the Tesla Powerwall is its design architecture of battery storage at LV, allowing for integration into many existing PV systems without the need for a new inverter, albeit at the expense of back-up power in the event of a grid outage. Back-up power may be of low priority for many consumers.

This dramatically reduces the overall cost of introducing energy storage to an existing PV system, and at the same time eliminates redundant equipment that may be only part way into its lifetime. It will be interesting to see if other manufacturers move in this direction.”



Question #2 Will solar and battery storage change the way Australian households and small businesses source energy?


Warwick: “Solar and battery storage will revolutionise consumers relationship with the energy grid.”

Xantor: “Definitely YES. People have been hanging out for a good storage solution for years.”

Muriel: “Solar PV has already changed the options available to consumers and more than 1 million households in Australia have chosen to source at least part of their electricity from solar.  As battery prices fall and feed-in tariffs for exported solar power are reduced, the option of storage with PV will start to make sense for an increasing number of customers.  This will increase the percentage of solar energy in our electricity mix, as it will facilitate longer periods of on-site energy use and hence larger solar systems.”

Luke: “Definitely. It is now cheaper to get power from your own roof than from a coal mine hundreds of miles away. But with the rise of renewable energy like rooftop solar, we need new ways to balancing the grid. With the GridCredits controller, you can help keep the grid stable whilst earning money. When prices spike in the wholesale markets this means that there is an engineering problem: a shortage of energy perhaps or the unexpected failure of a transmission line. By injecting power at this precise moment, the GridCredits controller automatically keeps the system stable.”

Geoff: “Most certainly it will. The transition to greater autonomy will be driven as much by the desire to avoid giving away solar energy to the utilities for pathetic feed-in tariffs, as it will the economic drive to save on energy costs. The economic analysis of energy storage points toward a sweet-spot of relatively small amounts of energy storage in residential situations, cycled heavily and worked hard, to maximise the economic benefits, leading to the shortest possible payback period. This probably means that the first wave of residential energy storage will provide low levels of autonomy, perhaps a step towards leaving the grid, but far from it.

It’s worth remembering that purchasing decisions are often made emotionally, backed up by rational arguments. This is evident with the furore of interest in the Tesla product, when it is not even available yet, and many consumers don’t even understand what it could do for them.

The desire for autonomy from the utilities may drive people to invest in energy storage well beyond the economic sweet spot; in my experience with off-grid solar, people who leave the grid just love it, many saying they will never return.”



Question #3 Will storage such as the Powerwall with solar panels make going off the grid financially viable in the long run? If so, how long before this is so?


Warwick: “If you’ve got a grid-connection. going off grid isn’t going to be financially viable for a long time… The grid is like a super-huge battery that costs a lot less than your own battery bank.”

Xantor: “It will. My guess is that it’ll take about 5 years.”

Muriel: “Cost effective and reliable storage will definitely make the off-grid option more feasible, depending on the regulations, and perhaps even penalties in place around doing so.  Going off-grid requires much more careful management, as well as minimisation of load.  So energy efficient buildings and appliances become more important, as does timing of energy use.  Based on the price projections being made by battery manufacturers, the off-grid option may be cost effective within 2-5 years; even less for an efficient household.”

Luke: “Reposit doesn’t think it is sensible to go off grid unless you are in a remote location. It is much better to work with Reposit’s partners so you can have a new, more rewarding relationship with the grid – buying when prices are low and selling when prices are high.”

Geoff: Leaving the grid is an entirely different exercise to maximising self-consumption of solar energy; it requires an entirely different level of autonomy.

The falling cost of energy storage will eventually make leaving the grid financially viable.

The financial viability of grid defection is totally dependent on the utilities tariff structures, relative to the falling cost of storage. The utilities may push consumers towards grid defection by raising fixed charges and introducing capacity or peak demand charges. The death spiral of the traditional utility is inevitable, however some nimble utilities will find new business in supplying energy to consumers from new technologies.

You’re after a time-frame. From what I read, I’m estimating we will see significant numbers of grid defections by 2020. The rate will depend on the utility strategy over the next 5 years, as well as the political response when the defections begin to be noticeable.”


Question #4  Will wind, solar and battery storage spell the end for fossil fuels as a dominant fuel source? If yes, how long before this occurs?


Warwick: “Fossil fuels are already in decline in our energy mix, but they still dominate. I expect that every house and business will have a solar system by 2030.”

Xantor: “This is a more complex thing.

In short, yes. It will take (my believe, based on my hope) 25 (electricity) to 50 years (all our energy consumption).

Just one more thing: The Tesla Power Wall is not designed to go off the grid at the moment. It’ll be easy to make them off-grid compatible, but currently they are only for on-grid storage.”

Muriel: “Wind and solar have already overtaken fossil fuels in capacity installed in many countries over recent years.  Cost effective storage will reduce concerns around intermittency and hence increase their market share.  

In Australia, some analysts have predicted that no new coal fired power stations will be built.  Many of our current coal plants are reaching the end of their expected life, while gas-fired plants are losing their market share in the high value peak period.  The prevailing policy drivers will determine whether old plant is retired or refurbished.  However, in the meantime, renewable options are reducing in price and certainly have a higher level of social acceptance so, for the electricity sector, renewables seem likely be the predominant energy source by mid-century.  

For the transport sector, the transition may take longer: a range of biofuels is under development, while a transition to electric vehicles is also dependent on battery developments which parallel those in the power sector.  However, once more of the transport fleet is electrified, renewable sources open up.  Since replacement times for cars are much lower than for power plants, the transition could occur quite fast once it gets going.”

Luke: “It already happening. Over 1000MW of coal generation has closed in recent years and the system operator predicts that there is another 10,000MW of spare capacity which will need to be closed in the very near future. At the same time it is expected that 20,000MW of solar will be installed by 2030, much of which will include battery storage.

The grid will be very different in 2030 with fossil fuels only used in special circumstances. We think that a viable mix is already available for the national grid; wind farms generating overnight, solar during the day and existing hydro and storage filling in the gaps.”

Geoff: Yes, renewables will replace fossil fuels eventually. Tony Seba‘s work on Clean Disruption of Energy and Transportation leads me to think that critical tipping points will be reached around 2020 to 2022 where Electric Vehicle deployment accelerates to the point of no return to fossil fuels. By that time, energy storage costs for stationery energy will have fallen too, and we will begin to see a dramatically different energy sector.”


Some fascinating and important points of view from our panel but do you agree with our experts’ opinions? Is there anything you’d like to add to the panel’s answers? Has this article helped you re-think the best battery storage for your situation? Please have your say in our comments field below.



  1. john nielsen says

    Hi Rich,
    I searched the web to find anyone selling the famous Powerwall. Only one in the US took orders, but didn’t sell any. I have a 6 kw PV system, Enphase micros. Enphase also promotes the AC Battery, but no one has seen one sold and installed yet. It is all hot air. I have 12 off 12 volt 250 ah lead gel batteries as I didn’t want to wait for that pie in the sky from Tesla or Enphase. With respect to the answers from the experts: As I understand it, the Powerwall, need an input of say 350 volt dc and has an output of about the same 350 vdc. It was stated that it could not be used off grid. Why not? I could transform the 350 vdc down to 48 vdc to feed my 8 kw inverter which is feeding my micros and load. My battery bank inputs 48 vdc to my 8 kw inverter which is on line with the load and the micros. Nothing connected to the utility grid. If you were to use the Powerwall as it is meant to be used, you would still need a grid inverter and be dependent on the grid to activate your grid inverter. I all seems a clumsy way to me. As for the Enphase AC Battery, maybe another pie in the sky. No doubt the future will be an alternative to the more than 100 year old lead acid battery, but I didn’t choose to wait for the unknown, but wanted to reduce my 6 member households quarterly electricity bill from $800 to Zero.
    John Nielsen, Silkwood.

  2. Hi Rich.
    As the Devil’s Advocate I remind you that in some previous posts I’ve repeatedly made the point that depending on consumption (which in most cases can easily be reduced by 50% or rather more than that) stand-alone solar-systems (battery-storage) have been more cost-efficient than grid-connections for quite a long while.
    Muriel pins it down in a sentence:- Going off-grid requires much more careful management, as well as minimisation of load.

    The fundamental consideration of ‘management’ is to avoid needing to store power where possible: easy in these days of very cheap panels.
    eg. Install enough panels to run all your heavy-users when the power is being produced.—-> run your fridge/freezers etc. flat out all day long and not at all at night.)
    Use a small demand-start generator to run the short-term heavy power-users (microwave, vacuum cleaner, washing-machine, power-tools ~ whatever) in order to avoid using battery-storage for those. A variety of proven-efficient-long-ago methods can be used to provide an essential amount of power on the occasions when the sun don’t shine. ( But keep in mind that ENOUGH panels producing even a modicum of their rated output, even on the cloudiest day, can still provide a lot of power.)

    …and there are endless ways to minimise consumption without being deprived of the necessities, which I’ve also blogged on. I speak from decades of having done just that ~ beginning when 2nd-hand panels were 10-15 times more expensive than new ones nowdays, and every watt counted….and WAS counted.

    Current arithmetic:-
    New, reasonably good quality AGM batteries can be bought anywhere for $2 per AH (12-volt) and getting cheaper all the time.
    But currently, that’s, roughly, about $200 per kw.
    Keeping the ‘management/minimisation’ (above) in mind 5kw storage ought to be ample to run an energy-conscious household. ie. an outlay of $1000
    Now double that to allow for contingencies and a lesser percentage of DOD. (which also means longer batter life. So:- 10kw of storage for $2000 (or less, since discount-for bulk is always available).

    Batteries, properly ‘managed’ should last five years. (or more: I bought 2nd-hand AGM batteries for $1 per AH which are still working well EIGHT years later)…. AND they’re getting both better AND cheaper all the time.

    GRID CONNECTION (leaving aside the question of spiralling power-usage charges) costs me $1.544 per day: ie, heading towards $600 pa.

    Bottom line:- At CURRENT rates I’d pay for an ample battery-bank for the same price as 3 years of grid-connection….BUT the battery-bank is expected to last nearly twice as long as that 3-year period, so I’d be saving $1100+ over the cost of grid-connection by installing batteries today.
    …and then keep in mind that the exponentially-increasing (and rip-off! by the retailers) charge for connection will be, given the record, well over $2 per day.*

    Unless one is an unthinking power-hog there’s no question that stand-alone battery-storage is not only the way of the future, but clearly the way to go today.

    When I had my system connected to the grid the FiT was returning me about $1600 pa. That’s been reduced by about 50%, though my usage etc. remains the same. I’ve told Origin that as soon as they stop sending me money I’ll get the bolt-cutters out and disconnect.

    My only problem then will be what to do with the excess power I produce, (‘management’) since ~ on an annual basis ~ I produce about three times as much power as I use.

  3. john nielsen says

    Hi Rich,
    What a great website this is.
    I see Jason’s and many other people who have raised the same problem, as what to do with the excess power, which I believe is easily solved. I have Enphase micros which automatically switch off when the voltage isn’t between 200 – 270 vac or the frequency not between 46 – 54 Hz.
    However I CONTROL the output from the micros to my load and 8 kw inverter/charger. Now, if you have a DC system between 150 – 400 VDC and a string inverter, you can do exactly what I have done: purchase a Morningstar relay driver with 4 outputs you can set the voltage threshold to whatever you choose. I have mine set to 12.20 volt min and 12.75 volt max. The relay driver reads the voltage from my battery bank, and if the voltage is between my set threshold, then the chosen channel on the M/Star is activated. I use a micro relay, 12.?? vdc (chosen)from the M/Star driver as coil voltage and output voltage 240 vac from the micro relay to a 40 Amp 240 VAC contactor which will switch on and off according to the battery voltage. Thus on a DC string system, I would have to use the same dp dt micro relay which tolerates around 12 vdc input for activation and a small, maybe 10 amp 240 volt output on the contactors, but you only need micro Amps to activate the large DC contactor which would switch off your line say 300 VDC from the panels to the inverter,,, and when the voltage from your small battery bank drops below your chosen threshold it will again activate the DC contactor line from your panels.
    I don’t have a string inverter system, but I don’t see why it would be any different from my micro inverter system. When my M/Star driver switches off my 240 VAC from the micros on the panels, it takes 60 seconds before they switch on again, and that is built into the micros, however on the M/Star driver you can change this delay to whatever delay you choose just not less than the Enphase programmed 60 second delay. I have recommissioned my old electric H/W system, and I now have free H/W from my 6 kw solar system except on a rainy day,,, when the voltage on the bats are below say 12.50 volt. I have set the H/W threshold between 12.75 high and 12.50 low as to give priority to the inside house loads. So with a relay driver, micro relay, and a suitable contactor, I cannot see where the problem is except that it will all cost you about $270 if purchased on the web. I have a 36 kwh bat bank and don’t use the grid even on a 3 week rainy period, But I don’t see why this system cannot be used on a one kwh system, as long as you have power to activate your grid type inverter. One important message: Whatever hybrid system you have, you must ensure that when connected to the grid, AND the GRID is down,,, there will be no way you can send power down the line to the grid. You can install a manual change/over switch in order that the load can only come from one place, either the grid or you hybrid system. This is what the generator change over switch is for. So for those who want to be connected to the grid, but don’t export to the grid, this is my 2 cents worth.
    Remember to use a licensed contractor.
    John Nielsen, Silkwood.

  4. Bob Johnson says

    In the 80’s I lived briefly on Macleay Is. At night the generators started up. What a relief when grid power came!
    I know things are very different now but going off grid could have similar problems. Where I live now it is not uncommon to have several days of drizzly, cold weather, visually no wind. No current battery could supply the high power devices that most of us consider essential-air con, heaters, driers,ovens,hot water,fridges,tv etc. Neighbors with generators. Noo!

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