Thinking about battery storage? Five things you should do first | RenewEconomy

Thinking about battery storage? Five things you should do first

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There is a lot you should do before getting battery storage for you home. Here are 5 steps households should take before making the leap.

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One Step Off The Grid

In April last year, we got 7.8kW of solar with a SolarEdge inverter, including consumption monitoring. In November, we got a 9.3kWh LG Chem battery. From this experience, we have learned a lot from the benefits of solar and independently, batteries, and think there is a lot you should do prior to making the leap into batteries. Here are 5 steps I think households should take before getting a battery:

1 – Add as much solar as you can

It is important to remember that batteries do not produce electricity, just store and shift it. On the other hand, solar produces electricity. The electricity can be used to power your household, and export to the grid. While many complain that feed-in-tariffs (10-15 c/kWh) are much less than what you pay for electricity (25-35 c/kWh), they still present a good return for your excess solar. Just on feed-in-tariffs alone, once can expect 8-12% ROI (annual savings/revenue divided by cost of solar installation).

We used to pay around $1,600 per year for electricity. With solar, we were earning around $110 per month in feed-in-tariffs, more than covering the cost of our remaining grid electricity usage, resulting in running at around $700 per year profit. With current high feed-in-tariffs, it is a good time to go big on your solar now to payback a good portion of your system in the next few years.

Feed in tariff credits

This could even mean getting 10kW of solar or more.

2 – Consumption Monitoring

It is important to have a good idea of how much solar you are producing, how much electricity your house is using and when, and how much solar you are using directly (ie. self consumption). Prior to getting a battery, we had shifted loads like hot water heat pump, dish washer and washing machine into solar production times to maximise our solar production. This saw us being 65% solar supplied! And only using 2-4 kWh per day from the grid.

So we knew that getting a 9.3kWh battery was a bit overkill for what we needed. But at least we knew. Without consumption monitoring, we wouldn’t have been in tune with our electricity demand and solar production to become 65% solar supplied, and would not have known what size battery we needed or if we needed one at all.

3 – Hot Water

Like many shire households, we used to have a resistive element hot water tank for out hot water. It was on a controlled load, and produced hot water overnight. We found that it was using 8 kWh per day. This was around half of our daily electricity use!

We now have a hot water heat pump. This is efficient and uses 2 kWh per day on average. When we got solar, we moved our heat pump production for overnight, to come on at 1pm each day. For watching our consumption monitoring, it is powered by solar for pretty much all of the year.

Photo: Heat pump (in blue) operating from 1pm

Basically, we are using solar to make our hot water in the middle of the day, then using the hot water when needed. It is effectively an 8 kWh battery.  A new hot water heat pump and tank costs between $2,500 and $4,500 installed, much cheaper than a Tesla Powerwall or LG.

Other than a heat pump, you could also use a timer to make your hot water system to make hot water during the day, or use a PV Diverter to power your hot water with solar (around $1,000).

4 – LED Lighting

We use lights predominantly at night. If you get a battery, it is wasteful to use up the battery capacity using inefficient lighting. It may mean that you get a bigger (more expensive) battery, or you leave less battery capacity available for back up or other purposes. Efficient lighting like LEDs can use 80-90% less than older lighting technologies.

5 – Electrify and be efficient

It is now possible to meet all your household energy demands efficiently using electricity. This may mean a heat pump for hot water, electric induction stove tops and ovens and efficient reverse cycled air conditioning for heating in winter. This means no more gas bill, and in particular, now more gas connection fixed fees. This saving on gas bills can help your payback on a battery. And even more, you can reach 100% solar supplied!

Rather than investing in a huge or multiple batteries, see what efficiency improvements can be made around heating, cooking and other uses, and see through your consumption monitoring what best battery may suit.

If would like to find out more about how to go all electric efficiently, the My Efficient Electric Home Facebook Group is a great place to get info, hear from others and ask questions. 

This article is by Jonathan Prendergast, founder of the volunteer-run Sutherland Shire Community Energy initiative (and website) Sunny Shire. He also contributes to My Efficient Electric Home Facebook group – a popular and active forum for Australians seeking to improve energy use in their homes. It was reproduced here, via Solar Choice, with his permission.

This article was originally published on RenewEconomy’s sister site, One Step Off The Grid, which focuses on customer experience with distributed generation. To sign up to One Step’s free weekly newsletter, please click here.


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  1. GlennM 2 years ago

    Yep…been through the same process and agree with the suggestions. HW heat pump, efficient appliances, LED lighting, as big a solar system as possible…..

    Then the battery is the final thing to do..only if you have done all the rest first

    • MaxG 2 years ago

      The battery has to be considered at the planning stage; otherwise the PV may not be big enough to recharge it.
      It is a system, hence, each component matters for the system to function properly.

    • Steve 2 years ago

      I would tend to agree with his points except that:

      We are limited by the amount of solar I can get on my roof;
      We are limited by the urgent OST of battery to purchase a smaller unit;
      Any draw on the grid in the afternoon costs more than 50 c kw/h so I charge my HWS in the late morning

      I would also favour exporting in the early morning until that morning demand spike is over

      • Greg Hudson 2 years ago

        Holy sh%$ 50c/kWh ? Where on earth are you that you are getting reamed like that ? (And by whom?)

  2. George Darroch 2 years ago

    How would an EV or PHEV affect the author’s setup?

    • MacNordic 2 years ago

      Will try to offer some ideas and suggestions – feel free to add/ correct!

      If the usage profile of the EV means the car is away most days (during the week): leave it as it is, as you will mostly charge from the grid/ public charger. Maybe add capacity to make up on FiT for the cost of charging, if possible (roof size, export limits, availability of FiT).

      If it is a PHEV or an EV with a smaller battery – or car usage is below ~14kWh/ day on average*, but the car is near the installation during most days: get a good, flexible system management system that maximises PV utilisation in the home and juggles the changing load intelligently while not using grid power. FiT credits would mostly be gone, though.

      If it is an EV with a large battery, add more panels if possible! The amount of panels should cover most/ all of the charging needs for most of the year, so if you need ~40kWh/ day, the surplus generation fed into the grid before (17.23kWh, green area of graph) should be 40kWh or more. If possible. Rest same as PHEV.

      If the FiT credits are a requirement for the future, add more panels, otherwise as before.

      If V2G is possible, you may be able to save on the home battery storage.

      General: run the numbers for a) average consumption in house and driving needs, b) max consumption and c) min consumption. Allow for seasonal changes, additional loads and have energy efficiency upgrades done/ calculated before to avoid having a system not fitting your needs. Get system cost for all three scenarios, check ROI and then with your bank manager;-)

      *The authors system shows 17.23kWh export at the height of summer. Lowest export might be around 12kWh. 14kWh or above for most of the year.

      • Greg Hudson 2 years ago

        ”FiT credits would mostly be gone, though”
        My thoughts on this: The FiT would be basically irrelevant if power going to an EV is chewing up your FiT because the alternative of using an ICE vehicle would probably cost 2 to 3 times to refuel with dino bones.

        • MacNordic 2 years ago

          Absolutely – just if you like the credits (and associated zero invoice sums) from the power company you should be forewarned 😉

          • Greg Hudson 2 years ago

            Perhaps you didn’t understand me… If you charge your EV instead of selling to the grid at a usually poor FIT, you would most likely be better off financially. This is especially true in Australia where Tesla will be charging (pun) users 35c/kWh at SuperChargers (which is WAY more than what it costs them – meaning that their ‘non profiting fees’ are complete BS).
            I’m just a measly single person, and I pay 18.6c (inc GST/VAT) surely Tesla must be able to buy at a much cheaper rate than I can? However, I digress…

  3. MaxG 2 years ago

    As a PV and BESS ‘user’, I’d like to add the following comments:
    1. (PV) this statement (“Add as much solar as you can”) is driven by human greed; I disagree by saying install as much solar as you need today, in the foreseeable future, and what you need to feed a battery if you want to go for a battery. The FiT could be over any time; then what… about your ROI?

    2. (Use) Monitoring should be the first step, optimising use (reductions) next, then load shifting. The size of the battery depends on what the ultimate goal is; e.g. shoulder cover, 24h cover, or longer.

    3. (HWS): Shifting HWS heating into the solar hours usually suffices to reduce the HWS bill to zero. HEnce, there is no need for a heat pump (still relative expensive for that it does). 8kW/days is certainly related to crap insulation of the HWS (which is simply a common theme in AU).

    4. (Light) = LED, a well known fact, related to point 2.

    5. Agree on this point; anything can be powered via elctricity; power tools, cooking — basically get rid of gas; which costs the same as electricity per kWh delivered.

    New 6. An EV would significantly change this set-up (or not), solely depenend on the time of use, and km driven. E.g. mum/kids use = increase solar to charge during the day; dad-use and long km commute, no change, as charge is cheaper from grid (hence, keep system the same).

    • Pedro 2 years ago

      As a rule of thumb for minimizing grid use with PV and a battery bank, I would tend to recommend having twice the average PV production capacity as the average daily load with a minimum battery size of about half the average daily load. It is good for people who want to stay connected to the grid. If possible I would have an east and west alignment of the panels.

      • MaxG 2 years ago

        Based on what?
        So using 23kWh/day = 46kW in PV? Battery = 11kWh?
        At a high-level I would claim the opposite: half the usage as PV, daily use as battery.

        • Jon 2 years ago

          I agree with Max’s first post & Pedro’s rule of thumb.

          Our daily usage is ~ 15kWh/day (full electric home with a pool), we generally generate ~ 25kWh/day.

          We’ve got a heat pump HWS and have changed as much use a practicable to self generation hours.
          We generally export 9-10kWh a day and import 5-6kWh.
          A 5kWh battery will cycle once per day and get a decent pay back, a bigger battery will let us timeshift power from a sunny day to a cloudy day but not have the same return on investment.

          • MaxG 2 years ago

            Your’re right… I misread; took generation for PV size. 🙁

          • Jon 2 years ago

            All good 🙂
            Enjoy your contributions and insight

        • Pedro 2 years ago

          For Perth I normally average PV production at about 4kWh/kW of PV. For offgrid system I use about 2kWh/kW of PV (which is June average daily production). Please note this is all back of the envelope stuff. Anyone who is going to be spending 10’s of thousands of dollars on an off grid system deserves a proper design.

          • MaxG 2 years ago

            Agree to the latter 🙂

      • MaxG 2 years ago

        Apology… I misread… you said double the usage as ‘generation’, not PV size… I can agree with that; have the same numbers; mean use 23; mean generation 46kWh 🙂

        • Pedro 2 years ago

          No problems 🙂

      • Jonathan Prendergast 2 years ago

        Another rule of thumb has suggested 1kW of solar for every 1kWh of battery. I think this is a bit over the top. On average, we generate 35kWh per day, and now have a 9.8kWh battery. We find during winter the battery struggles to get fully charged during the day on around a third to a half of the days. And we are at a ratio of 3.5 rather than the 2 you suggest. So I would suggest max out your solar as much as your roof and budget allows.

        • MaxG 2 years ago

          That rule is certainly wrong in Qld if you refer to 1kW of solar as solar installed. We have a 20kWh battery and a 10kWh (eff) PV system. The battery is on mean average full before noon.
          I’d say again, proper research before investing pays off (also taking location into account).

    • MacNordic 2 years ago

      Max, looking at your data may I suggest a change to your system management, especially the battery charging times?

      At the moment, it charges as soon as the sun goes up and provides the first electricity in the morning, precisely at a time where the generation is worth more to the grid, while shutting off around midday, when there is plenty of solar PV generated electricity in the grid. This also leads to a throttle on your generation, if I am not entirely mistaken, until the HWS comes on.

      If you could switch the charging to start at ~10:00, it would benefit the grid as well as your export possibilities, seeing you are at export limit for half the generation time – while at the same time having production restricted…
      Result would be a more grid- friendly production profile, better/more use of the PV generation asset and most likely even more FiT credits while helping the grid [static charge timing].

      Another possibility (if your system controll supports this) would be the prioritising of the feed in to the grid, and only once self- consumption and the max export in are covered, the battery charging starts (basically not a vertical cut in the charging profile, but a horizontal – the tip above 5kW goes to the battery) [flexible charge timing].

      Both ways would provide a better system utilisation to unlock the full benefit of the system and its incorporated energy from manufacture while greening the grid further. And be easier on the inverter/ panels, which currently have to take the throttling…

      • MaxG 2 years ago

        🙂 Sure you may…
        However, our priorities are different. First us, then the grid!
        Since we are in the sticks, where the grid is relatively unreliable (we encounter six plus hour outages say four times a year), our prerogative is to have the battery as full as possible at any time… hence, it will be charged as quickly as possible (though I limited it to Q/4).
        The FiT does not matter to us (as we are not greedy), and its only function is to offset the supply charges.
        Should the FiT end, we will get a 6kW/h generator and disconnect from the grid (as there is no benefit whatsoever to stay connected.)

        Our approach most likely differs compared to most, where peak smoothing or avoidance is the driver, and the grid connection is appreciated.

        • MacNordic 2 years ago

          The sticks& fail part explains it;-)
          So your system does not island on grid disconnection? Do you use your battery via a dedicated socket and manual plug- in on grid fail, then? Just curious…

          • MaxG 2 years ago

            Oops… I updated my post with (the system disconnects from the grid, but we remain with power); islanding from the grid on grid-power-loss is a legal/mandated requirement. But, due to the battery our inverter/charger keeps going… hence in case of sunshine, it can charge the battery and feed the property with energy.
            So, no — no weird or even illegal pugs and stuff; all hard wired.
            Imagine the inverter charger with three connections: the grid, the battery, and the property with its PV. If the grid does, it disconnects from the grid, but the whole place keeps going. As long as the battery has enough juice to keep the inverter/charger alive, PV will recharge/feed the property.

          • MacNordic 2 years ago

            Was wondering;-) but not trying to imply any illegal stuff – there are actually inverters with a socket instead of the UPS function you have, so one could switch fridge and (small) airco manually by relocating the plug…
            Do you have any idea how far back the change of the charging profile (like I suggested) would push the completion of battery charging? Just wondering with the curve on the shortest day looking like it does and reliable Australian sunshine…

          • MaxG 2 years ago

            Part 1: I didn’t understand, sorry.
            Part 2: If I were to reduce charging to extend the charging period to maximise export, I would still aim to finish no later than 14:30. I am not doing it, because any delay in charging increases the risk of cloud cover, then not being able to charge to 100%.
            There is always a trade off between options; our approach is solely related to the our perception of risk. While we are not paranoid about the system, we are very well aware of its performance. E.g. most people have an idea about inside or outside temperatures; we have a clear idea about the SoC, hence, we have figured over the years, that our approach works best for us (ou circumstance).
            As I mentioned before, FiT is secondary, energy ‘security’ (including stability and continuity) is our prime objective.

          • MacNordic 2 years ago

            No problem;-)
            On part two, I was just curious, seeing the graph and obviously very capable PV system you run. Fully understand your choice and you clearly have optimised it to your needs and requirements – hats off to you!

    • Jonathan Prendergast 2 years ago

      Hi Max, I agree that ‘fit as much as you can’ should include not just roof size, but what a household can afford. While getting a big system now sets them up well for the future, it should not be so big to challenge their finances.

      However, there are many good reasons to go big on solar and to do it now. I don’t think it is driven by greed, as it has been showing that rooftop solar reduces the number and severity of high prices events (more so in Vic and NSW) by increasing supply (generation) or reducing demand. By oversizing your solar, you may have excess in summer, but you are better placed to charge a future battery on cloudy/winter days. Also, STCs and market conditions are good now, so best to do it now rather than add later. (more reasons in article below)

      By suggesting monitoring first, you are also effectively suggesting holding off solar investment (to get more data I presume). There are many good solar monitoring systems that you can get consumption monitoring, so you can get this the same time as solar, and it is integrated. As above, conditions for households to get solar now, so the sooner they get it the better. The sustainability hierarchy used to suggests, reduce, by efficient, then generate. But the way solar has come, it can be the best starting point for households.

      • MaxG 2 years ago

        Thank you for your reply… I’d say our thinking is different, hence the difference of opinion, yet achieving the same outcome.
        My numbered response was directed at your numbers, adding my wisdom to it.
        The reasons why people do solar varies. While I am a socialist (as in for the community benefit) the minute the electricity market was privatised, it became a corporate product; and as such I have no obligation to support it; hence, I do not care about it. I do not care where prices go, or a spot price has been curtailed. The reason i went solar is two-fold: 1. remove myself from the leeches; 2. provide cost certainty on power (I will basically have no power bill until I die). — The only way (for me) to do it, was building an off-grid system that works… I only kept the grid connection as a generator, offset by some sort of FiT (as a quit pro quo).
        Heat pumps do not make the grade for a PV-driven HWS; as much as I appreciate their value. My HWS cost $700, and is fed by PV excess. Unless you give me a heat pump for $700 or less, it won’t be attractive, both, reasonable and financially.
        I do use a heat pump in form of a reverse-cycle A/C, which makes perfect sense.
        Also, I am not “effectively holding off”; any investment/purchase decision should be made with due diligence; hence, without knowing your consumption pattern, load shifting opportunities and day/night time loads, the decision should not be made. Since buying solar is usually not a ‘spur of the moment’ decision, data collection should happened during the process of preparing for a decision.
        I won’t argue about how long this takes; some take a year or longer, others a few weeks. I am sure if most would think and gather data upfront, they’d have better suitable systems.

        • Graeme Harrison 2 years ago

          I disagree that installing a large PV is about greed – it is more about sticking a finger in the air to the gentailers who have been purely about ‘greed’. The luscious irony is that it is THEIR greed that has pushed retail electricity prices so high, that ALL of their customers are trying to leave them! It couldn’t have happened to a nicer set of blokes!

  4. neroden 2 years ago

    My priorities were to (a) electrify everything, (b) add everything I was planning to use in the future, (c) make all of that as efficient as reasonable, (d) monitor the load profile, and then (e) add solar + batteries. But my grid electricity is cheap, pretty reliable, and already 100% renewable — not like your situation in Australia at all!

    • Rod 2 years ago

      Grid connected solar was a bit of an expensive attempt to do the right thing in the early days. The economics really weren’t there, even with subsidies, to contemplate getting a large array.
      As such, many early systems were between 1kWp and 1.5kWp.
      However, the experience of monitoring usage and export as well as the incentive to use less (export more) has given me a very good idea of how much PV and storage we would require to go off grid.
      I’ve just installed 6.6kWp and a hybrid inverter at a rental we might downsize to one day.

      I am very confident with a 10kWh battery we could go off grid if, as I suspect, FiTs are reduced and prices remain high.
      Of course, an EV would require a re-think.

  5. Coagmano 2 years ago

    Any advice on what consumption monitoring device to use?
    I’d love to have something with charts like you have

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