Thoughts on Solar + Battery System and Reducing/Eliminating Dependance on Gas

UPDATE:
I think I have all the info I need regarding solar + battery and may decide to hold out on the battery installation for a year or so after installing the panels depending on the costs of batteries by then. I would still like to know why it would be good/bad to not have gas in at the property

Hi OzB,

I will be having my first home built (in Victoria) by the end of the year. I plan on installing a Solar + Battery system soon after. My current average daily electricity usage at my rental is about 4.5kWh.

I plan to install a 3Kw solar panel system with a tesla powerwall battery for the new home. The panels should generate at least 9kW on average per day which would be more than enough for my needs. But I plan on buying an electric car in the future and I envision my electricity usage to increase in the future so I may choose to go for a 5Kw solar panel system instead. I assume that the excess energy that would be produced would offset my daily supply charges from my energy provider. Thereby, ensuring zero or in-credit bills. I believe such a system would cost about 15k to be installed?

Some points of note:

  • My new home is going to be significantly larger than my current rental with more appliances running (Big screen TV, dryer, etc)
  • Planning to start a family sometime next year so that would lead to increased electricity usage as well
  • I only have a single rate for electricity usage. No off-peak rates
  • Me and my wife both work during the day so there is hardly any power used in the household during daytime except for weekends.

I would very much like to not be dependent on gas at all but I guess that is not really feasible as everybody tell me that I need to have gas for room heating, water heating and cooking. Now in the two years that I have lived in Australia, I have not used gas ducted heating for the rooms yet and I am more than happy to have just a electric room heater running when I need it and I have no qualms about having an electric cooktop instead of gas.

My concern is regarding water heating as I'm told that instantaneous electric heating is not as good as gas. Apparently it takes longer to heat water with electricity and even then the hot water supply is not constant for long even if I have a storage tank (which is not good for me as I take long showers). Also, is it true that the value of the house, should I choose to sell it later, would be undervalued as people prefer gas cooktops and gas water heating? Please note, I will still have gas ducted heating installed for the house as it is a build inclusion but I just wont be using it.

I would like to know if my Solar system plan is not viable and also if having zero dependency on gas is stupid. I need to make a decision fast regarding gas for water heating and cooking soon as my build plan would need to be finalized in a week or so. Would appreciate your thoughts on this!

Comments

  • you either go off-grid (plus backup generator) , or don't bother.

    you're still paying supply charge with zero usage.

    you can sell back 'extra' electricity but feed-in rate is too little to be worth it.

    • Well I would like to be completely off grid but I worry that I'll be without power in case there is some issue with the battery or panels someday. I was hoping that the feed-in rate would offset the supply charge especially with the 5Kw solar system

      • A huge chunk of your annual electricity bill is just for being connected. So it will be charged even if you using zero or negative grid power.

        Buy a big diesel or petrol generator from costco for emergencies like if your solar panels get smashed by a falling tree.

        • If you say that the supply charge is $1 a day and a kWh costs $0.25 then using 4kWh a day means it's a 50/50 split between supply and usage. If you use 20kWh a day then your supply charge is 20% of the total bill cost.

          It isn't actually too complicated to do a comparison because there are some costs for a generator that you end up paying whether you use it or not e.g.

          cost of generator
          cost of fuel
          cost of getting the fuel (transport)
          cost of storing the fuel
          replace fuel regularly (as it doesn't have an indefinite shelf life)
          cost of consumables (oil filter, oil)
          cost of servicing the generator (assuming you can't do this yourself)

          Once you start adding all of that up (and somewhere in there, you factor in your time), paying $365 a year in supply doesn't look anywhere near as bad, even if you never use it…

  • How much would you be saving by not having gas connected? Is there a large cost to get it connected?

    • I'm not very sure how much I would be saving by not having the physical infrastructure for gas installed and I don't suppose it would be a lot. I am more concerned about the savings by not having actual gas supplied to the residence which would be about $90 per quarter even if I don't make use of it.

    • +1

      The gas supply charge will be about $300 per year.

      • +2

        So cheap! I'd be tempted to keep gas connected (ditch the electricity grid tho). Gas cooking is always better.

        Gas heating is cheap, but what about summer?

        IMO anyone building a new house is crazy not to spend the extra 5-15 grand for ducted AC (it's much cheaper installation if the house is still being constructed, and that's a big part of the cost).

  • +1

    If you don't think you'll use gas then don't get it connected. You have to pay a supply charge even if you don't use it. See this thread: https://www.ozbargain.com.au/node/353516

    Solution for long showers would be a larger hot water storage tank.

    I love my instant gas hot water and I love my gas stove cooktop and it was one of the things that pushed the house I bought above the others, so - yeah I think it would affect the value of your home when you go to sell it. But if you're building it to live in it, get what YOU like and don't worry about the selling value, you're the one who has to live in it for the next ten+ years or whatever.

    • Thanks for sharing the link. Interesting read!

      So while some people said that a supply charge would still have to be paid just for having the gas meter there even if gas is not used, the OP for that post and another OzBargainer said that they were able to cancel the gas connection and not pay for supply charges. Things have changes maybe?

      • +1

        If you don't start an account with an energy retailer I don't know who would charge you?

        I know that when our house was built (SA) we didn't have a meter installed with the build - it was up to us to phone an energy retailer (origin, AGL, etc) and have it put on. I can't imagine that if you choose to have all electric appliances they will put any plumbing in for gas, unless you paid extra for the provision.

  • +6

    Have had a quote with Metricon and will be building with Burbank so definitely possible.

    The gas lines will still be pulled to the property from the street, however you don't need to activate it and pay the daily supply charge. Your builder should also provide you with a (very small) rebate for the gas hot water and gas heater. From memory mine was only a few hundred for both.

    Water Heating - Look into Heat Pumps, most builders will only give you the choice of Chromagen/Midea, this is ok but I will change mine to Sanden once it fails (5 year warranty with Chromagen/Midea). Heat pumps are very efficient and should actually be cheaper to heat water as compared to gas.

    Cooking - Lots of people are using induction cooktops now, it is more efficient in converting energy into heat as compared to gas, keeps the cook cool and boils/fry quicker than gas. If you are not sure just buy a cheap portable induction cooker and test.

    Space Heating/Cooling - You have two options here, either splits or ducted. Splits can be cheaper but some people don't like the internal look and also that they might need more than one compressor depending on number of splits required.

    For ducted systems have a look at Actron Platinum Que, this is the one I am going with. Not cheap but will allow me to have up to 8 zones with individual temperature control in each zone and can be controlled via an app so will only have one master control for a two storey house. Will be using phones with app to control when in the rooms and use a tablet for downstairs/guest.

    Good luck!

    • Thanks for all that info! Will look all of that up :)

      • Your welcome, you might need to move quick though. Actron took about a week to quote up everything so you might want to let your builder know in advance as this will likely delay your contract signing!

        Let them know in advance the number of zones etc that you want together with the fact that you need individual zone sensors not zone controllers. my quote for a 40 square house was just over $20k, my quote for the same house using mitsubishi splits came back around $16k.

        • The Actron Platinum Que does both heating and cooling? I was just planning on having inverter split A/Cs installed for the rooms, as I figured that would be cheaper in the long run and more easier to work with as it eliminates the needs of zones and such.

        • Btw, i'm building a 29 sq house. At 40sq, your username does not check out :P

        • @0FoxGiven: Yes, it does both. The inverter splits can also heat and cool so you don't need the gas heater at all.

          Splits are definitely cheaper but downsides for me when I was making the decision was the look of having internal wall units, needing 2 compressors to power the splits required and servicing all the splits will be a pain. Having Wifi control is possible with splits but can be expensive as you generally need an additional module for each split.

          The Actron system allowed me to have all duct with no wall units, Wifi control, easier servicing - essentially just looks better and more convenient. The external compressor is huge though, looks like a commercial unit.

        • +1

          @0FoxGiven: At 29sq you would likely go for the smallest, however will likely still cost around $13-$15k. I bought the house hence I am now poor….

        • @0FoxGiven:

          No no no, splits are definitely a lot more expensive in the long run, both in terms of maintenance (3 cheap compressor units instead of one quality one, 3 year warranties instead of a 25 year one, etc) and power bills.

          Plus the uglier look, more noise, less comfortable airflow, etc etc…

        • @iampoor: I sent you a PM.. please reply at your earliest convenience as I really need some first-hand advice on this

    • Space Heating/Cooling - You have two options here, either splits or ducted

      You're spending hundreds of thousands building a home, splits should NOT be an option. Ducted costs as little as 3 splits, is quieter, looks nicer, works better, costs less in power and maintenance, adds value to the home etc, etc…

      I will never buy a house without ducted AC again.

  • +1

    Is your 4.5kWh/day figure in an All Electric situation (I expect not), you should probably double that figure if you're going to cook, heat water and air con all electric Even then it'll be a conservative number in the depths of Winter.

    Otherwise it's probably a reasonably sound plan.
    You'll likely draw from the grid on overcast days, but if you can get a good time of use deal on your power to recharge the battery with cheap grid power, then that'll help minimise your grid power bill.

    We use around 12kWh/day on average (with Gas cooking, hot water and heating), so you're an energy miser. We have a 5Kw System (2kW North, 3kW West, no battery) and we get paid maybe $200 through Summer and Pay around $600 through Winter.
    Overall probably pay out around $400/year.
    I suspect that if we had 2kW East and 3kW West we'd be better off as our peak power tends to be first thing in the morning and in the evening. With reduced usage through the day.
    Ideally you weant to use to power as you generate rather than charge a battery then use it later and lose 20% of what your panels made.

    • Actually, I only use gas for cooking and heating water at the current 3 bedroom rental home and my summer usage peaked at slightly above 9Kw only on two days when we had guests stay over on two particularly hot days. At my previous 1 bedroom rental apartment, gas was used only for water heating and my electricity usage was under 4Kw on average.

      So yes i'm an energy miser but then again its just me and my wife and all our appliances except the AC and Dishwasher (both of which we hardly ever use) have an energy rating of 4 stars :)

      • We use 3kWh/day on "vampire" power alone!
        Even being particularly aggressive at turning non-essential stuff off at the wall I can only get down to about 2kWh/day when we're on holiday.

        • +1

          I have xiaomi smart plugs for all my appliances except the fridge and wifi router. They cut off power when I'm not at home. So its just the plugs, the Xiaomi Gateway and those two appliances on Vampire power :)

  • +1

    My two cents worth….

    I would consider getting a 6kW array with a 5kW inverter, a battery and several small split system inverter air conditioners so they run on low all the time during summer set at something like 25 degrees and maintaining a low base temperature in winter such as 15 degrees throughout the house 24 hours a day then only use a gas heater (no central heating) in the living room to increase the temperature up to 20 degrees when necessary.

    Very very expensive…but you'll get very low energy bills.

    • Why 6kW with array 5kW inverter? I thought it was common to over-rate the inverter to allow for more panels to be added later?

      • +1

        It's not economical to add panels later.

        I would install as many panels as possible upfront.

        5kW is usually the maximum inverter that can be installed on a single phase supply. If there are 6kW of panels then around midday for an hour or two during summer then yes the output will be trimmed to 5kW but most of the time you'll get a little bit more out of the 6kW of panels so you may as well put in 6kW of panels if you can.

        • +1

          Plus you are talking max here, its very rare for any 5kW system to even get to 5kW at any time. In the heat of the day, the power can get reduced as too much heat and the panels shut down. (Or whatever the correct term might be)

    • throwing another 2 cents in the mix…

      what time(s) of day are you using your power? If it is mostly morning and afternoon, then look at an inverter (5kW is usually the maximum you are allowed unless you have 3-phase, or are completely 'off-grid') that has two 'strings'. Place one string / set of panels (say 2.5kW) facing due east, and the second string / the rest (4kW) facing due west. The total 6.5kW is because you are allowed (in most areas) to put up 1.33 times the inverter capacity in panels (when you are 'on-grid').

      This means that the times you are home (morning and afternoon) and using the power will be the times your panels are generating the most - thus saving you the most. The generation will dip as the sun moves from east through due-north - but that's ok, you're at work and the house is not using as much. As the sun moves to west, the generation will pick up again, just as you are getting home and start using the power again.

      Additionally, feed your excess into your hot-water storage system. Then into battery storage, if you can afford it - currently the payback period (11 years) is a bit longer than the expected life-span (10 years).

      Only then feed the excess back to the grid. i.e. you have sucked every last benefit you can out of your generation, and the grid can have the dregs.

      .h

  • IMHO batteries and solar are a bit overrated. Battery life will deteriorate just like your smartphone. Even then they might be good for only 10 years before needing replacement or serious maintenance. I would wait a few more years before jumping in.

    It's also arguably worse for the environment considering all the "fossil fuels" consumed just to mine the lithium etc, and then you have to dispose of it afterwards.

    https://youtu.be/17xh_VRrnMU

  • +1

    So much info already provided. I would recommend that you walk before you run. Install the minimum, then add to it in the future. So install the solar panels, but don't install a home battery straight away. Batteries are improving at a rate of knots. The Telsa 2 Powerwall is the same price as the Telsa 1 Powerwall - but double the capacity - and that happened in about 18 months or so.

    To use an apt comparison:

    Don't get stuck with an iPhone2 for 10 years, when people who have an iPhone5 are quite happy to stay put, regardless of the new iPhone7, 8 and X.

    And on the hot water front - you can also get solar hot water diverters. These divert your excess solar generation to heat up your hot water.

    • Will look into solar hot water diverters.

      I don't completely agree on waiting for things to improve though. Tech will always be advancing but the more you wait the more you could lose out as well. For example, Some friends of mine installed solar panels at their homes 7 years ago when people told them to wait for newer tech to come out and till things gets more mainstream in Oz for solar. And apparently, the ROI of the system paid off the costs in just 3.5 years due to the high feed-in rates they used to get. That would have not been possible if they did the same today with the low feed-in rates and higher electricity costs, it would have probably taken 6 years or more to get the ROI.

      Anyways, I will be looking to install the Solar + battery system only in 2019 and hopefully there will be better and cheaper battery systems in the market by then. If there there is news of better batteries coming into the market by say.. late 2019 or early 2020 then I might just install the panels and hold out for the battery.

  • +2

    Ok just some thoughts on your battery.

    Its probably too early to buy this. Wait to see how you use your system and how much it saves before going down the battery path.

    That way you can see what your usage patterns are and whether the battery system will be economical for you. Charging and recharging also decreases the life of the battery. If you get an electric car sometime in the future, my guess is that you will be charging it overnight. So the only way will be to import from the grid or from your battery system. Given in this case your main use of the battery is going to be at night, Off peak rates are really what you will be saving with your battery. Batteries really only are economical for those who use it to save Peak energy costs (like those at 60c vs the 12c off peak)

    So again, trying to work out if you need a battery without the data of what you generate and when plus how much power you use from the battery at any given time, isnt the best way.

    Oh an BTW the prices of batteries as other's say are coming down, so you gain on that side

    • Well I have been studying my electricity usage for the past 2 years and considering the fact that my costs are increasing steadily due to moving to a bigger rental home and rising electricity costs; a Solar+Battery system looks good to me on paper. Also, I dont have off-peak rates for electricity where I am. I have updated my post with a few points of note.

  • Batteries should drop in pricd in the next couple of years, so get a set up for now that enables you to add more panels (if you want) and a battery later.
    No point spending 5+ thousand on a battery now for a car you don't have yet.

    Something like a solar edge system with optimisers is a good system which let's you add on later.

  • Our 4kw solar system provides about 20kwh per day of power. a 5kw system sounds like overkill if you only use 4.5kwh per day. You need to design your system to be off grid compatible for your usage, even if you connect to the grid for 'backup' and so you can sell back.

    Consider electric storage hot water and pump your spare solar capacity into heating the water. We have that option, but our water usage tends to be in the evenings and since the unit runs off peak, I don't think we would save much by topping it up during the day when the water is already heate and in the event we have not enough solar I don't want the water to be heated during the day on peak power pricing.

    Spend some extra time designing your house for passive heating and cooling to save energy costs.

    Sounds like you need to do some more analysis of your situation.

    • You're further north, so your angle of incidence to the sun is better for longer.
      My 5kW system in Adelaide generates around 35kWh on a cloudless day around the Summer Solstice (longest day), but at the Winter Solstice, it'll only generate 14kWh on a cloudless day. As you go North, your days get longer and the angle to the sun gets better.

      • +1

        This is true. Our panels are not at the optimum angle and are split between North and west facing so are not at peak efficiency either. It averages about 20kwh per day. Peaks at about 25kwh and about 15 in winter.

      • A general rule is: multiply your system size by 4 - and that's your average annual daily generation - so 4kw x 4 = 16kWh per day. In QLD it's a little higher, in Tas a little lower.

  • I doubt 3kW is going to be anywhere enough to charge a Tesla on overcast days or the winter.
    Assuming here that you have no shading.

    • +2

      It wont fully charge from zero in the middle of Winter, even with all North Facing panels and no shading.
      But then at only 4.5kWh/day OP doesn't need a fully charged pack to get through a day.
      On an overcast week, they might need to charge up the pack with offpeak a few times. Otherwise, it's unlikely the battery would ever drop below 50% charge.
      With Victoria having (mandatory?) Smart Meter's, I wouldn't be surprised to learn that the Powerwall can be programmed to buy in cheap power automatically if necessary.

      • Yup.. As Scubacoles said, I would almost never need a fully charged pack to get me through the day. Not considering the electric car, even a 3 Kw system would be able to fully charge a 12Kw battery ( which already holds some partial charge) during the day when there is hardly any power usage.

        W.r.t to the electric car which may or may not be a Tesla model 3 (just something I covet, depending on my situation at the time, I may not go for it) with a 50Kw battery, which would not be purchased till maybe 2020, I would most likely just charge the car only once a week at the most.

  • Just wondering, Do you have to declare anything made on a feed in tarrif as earnings on your tax return ?

    • Yes I believe so..

      According to the ATO:

      "The taxpayer will be in receipt of assessable income in the form of the quarterly feed-in tariff payments made by the electricity retailer in respect of the electricity generated and fed into the electricity grid from the solar system on their rental property."

      • +1

        Key here is Rental Property.

        A domestic only system wouldn't be seen to be taxable, unless it can be shown you installed it to make a profit.

        https://www.energymatters.com.au/rebates-incentives/feedinta…

        If you are a pension, its generally not deemed income unless the following is true.

        Centrelink says feed-in tariffs paid as cash will be included under the income test over 12 months. For example, if a beneficiary of Centrelink income support payments receives a cheque from their electricity company for $260 it will be counted as $10 income per fortnight for 26 fortnights

      • How about if you buy power offpeak, store it in batteries, then sell it during peak time?
        Do you have to pay capital gains tax on that?

  • +2

    I kinda regret getting gas hooked up to my home too - should have got an electric instant hot water system (e.g: https://www.stiebel.com.au/water-heaters), an induction cooktop and reverse cycle ducted heating/cooling (rather than a gas heater and normal AC). Mainly because the price of gas is just skyrocketing here in Victoria.

    With my 6kw of panels, I only paid around $750 for electricity in 2017, so if a battery costs $10,000 and manages to take me off-grid (a $10k battery these days won't be big enough for that right now), that's a 13.5yr period until payback. So I still wouldn't bother with a battery just yet. I'd need capacity to double and prices to halve before I even bother seriously considering an off-grid battery. Better investment to get rid of gas from your home than bother with a battery.

    • Ok so just by quickly running your numbers, at least $370 of that $750 charge is due to supply charges alone. So the remaining $380 is a result of your usage charge which would equate to only about 3Kw of daily power pulled from the grid. This is of course not considering the reduced amount due to the feed-in rates you are getting, so maybe you are actually pulling 9Kw (just a noob worst case guess estimate without doing any math) of power from the grid on average daily.

      Do you use a lot of power during the daytime? If not, wouldn't a fully charged battery (seeing as you have a 6Kw panel system) that could store 12Kw ($10k worth) actually be completely sufficient to take you off the grid?

      EDIT: That noob math didn't consider any discounts you are obviously getting on usage charges. So my numbers might be off

      • If not, wouldn't a battery that could store 12Kw ($10k worth) actually be completely sufficient to take you off the grid?

        It would go pretty close for me… BUT it doesn't make economic sense yet.
        Probably need another 25% decrease in the cost of the battery to make good economic sense (assuming power prices don't continue to increase… obviously the maths change if they do increase further)

        • Ye I hope we see that 25% decrease in price by early 2020 :D

      • +1

        Sure, a $10,000 battery would take me off grid, but if I'm only spending $750/yr on electricity, the $10,000 I spent on the battery won't be recouped for 13 and a half years. That's a pretty shitty investment if you ask me.

        If the battery was say, $5,000, the payback time is still 6.7 years. Better, but still quite a while and if the cost of electricity continues to go up.

        Also with batteries, there's the issue of peak output. The Powerwall 2 for example, can do 7kw peak, 5kw continuous. If you've got an air conditioner that uses 4kw, which is on whilst you have the kettle going (1.8kw )and the missus is drying her hair (2kw), the battery will trip a breaker as there's not enough electricity to go around. You can get two batteries though, to alleviate that - but that also costs more, hah.

        So yeah, batteries are cool, but not yet. Needs to come down in price by 50% and supply more peak power (10kw imho, 7kw continuous) so as to not adjust my lifestyle to work around the limitations of the battery.

        • +1

          Also with batteries, there's the issue of peak output. The Powerwall 2 for example, can do 7kw peak, 5kw continuous. If you've got an air conditioner that uses 4kw, which is on whilst you have the kettle going (1.8kw )and the missus is drying her hair (2kw), the battery will trip a breaker as there's not enough electricity to go around. You can get two batteries though, to alleviate that - but that also costs more, hah.

          The whole idea with going solar is to first cut down your consumption, then determine what you need to supply. Work out how not to use the AC, kettle and hair drier all at the same time first.

          The other thing to consider with batteries is the payback period vs the warranty on the battery. currently the warranty is shorter than the payback period, so your batteries are likely to need replacing before ou have paid for them.

        • +2

          @Euphemistic:

          I can cut my consumption, but that doesn't mean that the scenario of me using the AC, kettle and hair dryer at the same time is going to go away. For me, the aim of solar & battery is free electricity (once the initial investment is paid back), not cutting consumption to the point where I need to make sacrifices.

        • @decryption: Don't need to sacrifice the comforts, just need to manage them better. Working out how to live without running the AC 24/7 is the first one (not saying you do this). Getting used to temperature not always being 22 isn't that hard.

          I'm in your camp though, we could cut our consumption at home some more, but then I'd have to turn off all the devices at the wall, or set up some sort of home network to activate things without bending down to floor level or reaching behind the tv unit everything I want to switch something on. All our appliances are already fairly energy efficient.

        • @Euphemistic:

          Then there's the cost of setting up all that in-home smart junk. I don't think it's worth spending say, $500 to get every outlet or switch to be intelligent, only to save like, $5/m in electricity.

        • @decryption: $500? I got all of mine for less than $60 (Xiaomi plugs on deals).. My daily usage dropped by a little more than 1Kw after going all-plug-smart. The costs of all those plugs would be recouped in less than 10 months for me.

        • Good point about the peak output.. I hadn't considered that

  • -1

    Somebody probably already said but maybe consider :
    Go the 5kw+, you can program the dishwasher , washing machine ect to work while you're out during the day
    Solar Hot Water system
    90 kg gas bottles for cooking ect

    Also if you have the time for it
    small wood fired oven for Winter especially if you enjoy chopping wood and having a fire like most people do

    • I'm sure that of the people that enjoy having a fire, the majoirty would not enjoy chopping the wood.

      • Because you city folk are soft and lazy
        Nothing like 4wdn through the forest with ya chainsaw and bluehealer when you spot a nice dead standing piece of timber
        I leave chopping it up to the kids

        • +1

          My point exactly. You enjoy handing the actual hard work to the kids, not doing it yourself.

        • @Euphemistic: actually it's so easy ,even the kids can do it

        • -1

          Because you city folk are soft and lazy

          Most people in Australia live in a major city.
          Most people in the city don't enjoy chopping wood.
          Therefore:

          small wood fired oven for Winter especially if you enjoy chopping wood and having a fire like most people do

          is false :p

        • @idonotknowwhy: if you can't see the humour in my posts , I'm not going to walk you through it
          PS. I suppose it's more of a man's (n tough chicks) skill ,
          so not for pussys

  • +4

    Go Heat Pump for hot water and program to heat during day when the solar panels are producing. Gas prices are not going down anytime soon and many are going away from gas because of the price.
    Cheaper to put bigger solar system in now rather than add later. Batteries are still not economic but will in the near future so add later.

  • +1

    As you're in Victoria, if you're in a gas reticulated area, a new house is required to heave either gas boosted solar water heater or a rainwater tank (or reticulated rainwater supply if available). If you want to go down the electric only, which is where housing will head in the future, then you will need to install a rainwater tank.
    Avoid electric resistance water heating, it's the most expensive option over the life of the unit even off peak.
    Heat pump water heaters are cheap to run and you can get them installed cheaper than alternatives by taking advantage of VEECs and STCs.
    Reverse cycle air conditioners sized appropriately are also the best option for heating, again avoid electric panels.
    PV can pay for itself depending on your finance, electricity rates and use so should be sensible if you put some thought into it.
    Batteries and smart controllers are still in their infancy, while cool to have and no doubt will take off soon, if you're just looking for cost purposes then they're not quite there yet. If it's environmental reasons then you can also purchase green power from your retailer at a slightly higher cost than regular rates.

  • How do people manage to average 4.5KWh/day? I average about 8.5KWh/day in summer and 12-12.5KWh/day in winter. And that's with only 2 people in the house, ducted gas heating/AC, gas cook tops, and LED lights everywhere. I thought my consumption was reasonably low, but 4.5KWh/day??? Just running a fridge will consume almost 2KWh/day.

    • And here I was sad that my daily usage went up from 3.5kWh in the old rental place to 4.5kWh in the new rental place. You make me feel good about myself :P

    • They must eat out and have their mums do their washing.

      • Hardly ever eat out and Mum is on another continent :P

  • +1

    It's been interesting reading all the comments.

    It'd be useful to note that you measure usage in kWh (not kW) - one is energy consumption measured through time where the other might refer to peak usage.

    We have a 7.5kW solar system coupled to a 13.5kWh battery. We've been running this for around 6 months now and it has worked well.

    We still maintain a grid connection - but it is basically treated as the 'backup power supply' and it works pretty well.

    To echo what many people have said, solar by itself is very economic but batteries less so - You want to size your solar system based on:

    • How much roof area you have available
    • How much money you can afford to spend
    • How much you energy you consume (per day)
    • How much you can feed into the grid (e.g. in NSW this might be a limitation of 5kW or in a 8 hour day, a maximum of 40kWh you can feed in)

    The battery cost (as it has no incentives or rebates) significantly reduces the ROI/increases the payback period but does make the solar look even better as the ability to use solar energy when the sun isn't shining makes it much more efficient.

    I'd always keep your grid connection (and gas connection) and pay the supply charge as these are useful for backup and also for changes you may make in the future.

  • The economics of a battery system are based on 1 to 2 full cycles per day. Even then the current prices make it not economic, and this is from speaking with people high up in the retail and distribution chains. Either wait, or install a smaller battery system (obviously not a Tesla).
    Suggestion: Get someone to engineer your system.

    • Suggestion: Get someone to engineer your system.

      A lot of this. While the solution is fairly simple (battery size and panel array size) getting the right sized system requires a fair bit of information on usage (past and future), sun access, roof orientation etc. If your supplier asks what size you want without first assessing your usage and other aspects, find someone else.

  • Ex-Gov.(Remote Solar)Batteries can be had at auction.
    Also blemished (slight mark on casing)deep cycles , can be had at least 50% discount from car battery factorys.
    build your own lead acid bank cheaper?

  • I am in the same boat. I’m building a house and decided that I wanted to have no gas. I am going to install solar as soon as the house is complete. I am undecided on which stove top to get between electric and induction, Although induction is the better choice. I am going to get an electric hot water system with a heat pump and reverse cycle ducted (with zoning) electric system for heating and cooling. I will get a 5kw but will not yet install a battery and I will have my bbq with a gas bottle incase of a power outage. I am trying to be more eco friendly as well as save money in the future.

    • is there anyway you can exchange your gas heating and get an electric reverse cycle as I think that would suit your needs more and if you can then definitely get a 5kw system :)
    • Hey KatM,

      I'm currently facing a lot of issues negotiating with my builder to go all electric. The builder is charging approximately 4k higher than what it would cost me to install ducted reverse cycle system via a third party. I don't even want to go via the builder for this as I wouldn't trust the quality of the work and the brand used. They are not agreeing to give me a rebate by taking out gas heating out of the cost either because they say the house has to have heating to get a occupancy permit/certificate for the build. I'm in a mjor dilemma on how to proceed with this at the moment.

      As for the cooktop.. Definitely go for Induction! I don't want to go with the builder installed cooktop because they are asking for 2.9k in upgrade costs, which I think is bullshit considering that the cooktop brand is Technika (90cm) which is like the cheapest one out there and that price is after the rebate I get for taking out the 90cm gas cooktop that was included in my basic quote. I'd rather get the 80cm Ikea cooktop and have it installed by an electrician.

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