Advice on Full Solar Upgrade - Solar + Battery + EV Charger + Hot Water

bobbieb on 13/06/2023 - 21:15

We've found ourselves in a position where we're looking at potentially going all-in on PV tech for our current house, but are getting lost on the conflicting - or at best, one-sided advice from various folk. I'm hoping for some real world experience and advice on what may work best for us.

So here's the situation… we have single story house in Sydney with no solar, and an old gas continuous hot water system that is long overdue for replacement.

We're also long overdue for a car upgrade, so will potentially be looking at EVs real soon.

There are a lot of articles, videos etc online that talk about adding one or the other of the above to an established system - dealing with the various challenges involved, but we haven't had much luck finding anyone talking about what a good full solution looks like using today's tech.

What does good mean to us? Ideally, lots of smarts… fast charging an EV optimally, while maximising feed in & minimising any draw from the grid. A good hybrid inverter that can keep the batteries charged & the important stuff powered in a blackout. A new hot water system that integrates nicely with it all.

The hot water question has us most confused. Heat Pumps seem all the rage, but from what we can tell, they might not make sense as part of a larger solar setup. Some seem to suggest that a old-school electric hot water system + a timer/diverter may actually work better.

Anyone been through something similar recently? As a bonus, we'd love to find a supplier in the Sydney metro area that can design, install, and support this sort of system.

TL;DR - We're looking to do Solar Power + Battery + EV charger + Hot Water in one go. What's the ideal setup using the latest and greatest (not necessarily looking to spend stupid money, just a bang for buck system that works together well maximises self use and feed in.)

Electrical & Electronics Hot Water System Solar Energy System

Comments

  • mskeggs on 13/06/2023 - 21:53
    +1

    I’m in the midst of this.
    I’ve gone with an old school hot water, as the extra cost for a heat pump isn’t warranted if I can have enough solar PV panels.
    We have 3kW solar now, I’m looking to add probably 8kw, to heat water, run RC AC as our main heating during the day and probably add a battery too.
    The financials for the battery aren’t compelling, but I can’t see power prices falling in future.

    Charging an EV is really very dependent on your circumstances. If I replaced my car, I could probably charge it from a 1kW system, I drive so infrequently. But my spouse does 200+km per day for work, and would mostly charge at night…
    So I am leaving that out of the equation for now.

    Get some quotes from a few local installers, look around on Whirlpool etc. to check any brands that might be known as unreliable, and don’t pay any extra for options you might use in future, chances are they will be cheaper by then.

    • bobbieb on 14/06/2023 - 06:58

      I’ve gone with an old school hot water, as the extra cost for a heat pump isn’t warranted if I can have enough solar PV panels.

      Thanks. This seems to be the way we're leaning. Spending on extra PV capacity on the roof, over a heat pump hot water system seems more flexible.

      I drive so infrequently. But my spouse does 200+km per day for work, and would mostly charge at night…

      We're a dual car household also, neither of which drive that often. But we're mindful that slower charging makes juggling two cars a lot more painful.

  • LVlahov on 14/06/2023 - 00:01
    +1

    If you are a high energy user, installing 5kW or less of panels go with the heat pump hot water, with its lower energy draw it leaves more for the rest of your needs and less likelihood of drawing from the grid. If you are a low energy user installing 5kW, or installing well above that (regardless of usage profile) you are probably fine just with a regular electric hot water heater.

    Can't help with brand names and particular solutions but thought that might make help with one element of the decision. We have electric boosted solar hot water on a timer and 3kW of panels, and I can tell you in winter the system still really likes to suck down the juice and it sees us having to buy from the grid, and the cost of that alone would have made it a better choice for us to go with a heat pump over any other solution. You'd only want PV feeding a non-heat pump hot water system if you had significant excess, and a regular excess throughout the year, not just part of it.

  • bobbieb on 14/06/2023 - 07:03

    If you are a high energy user, installing 5kW or less of panels go with the heat pump hot water, with its lower energy draw it leaves more for the rest of your needs and less likelihood of drawing from the grid. If you are a low energy user installing 5kW, or installing well above that (regardless of usage profile) you are probably fine just with a regular electric hot water heater.

    We have low to moderate usage. So it sound like the go would be a larger initial solar capacity on day one, giving us hopefully enough power to raw power to handle a regular hot water system with the battery for smoothing?

  • Overclocked91 on 14/06/2023 - 07:32
    +1

    A 6.6-7.7Kw solar system (Fronius-if budget allows. Otherwise Growatt or Goodwe) with a minimum 10Kw battery. Heat pump hot water system (310L) with a 3 Phase EV fast charger (if applicable-might not have 3 phase).

    How many bedrooms and people living in the house (approx.)?

  • bobbieb on 14/06/2023 - 07:39

    with a 3 Phase EV fast charger (if applicable-might not have 3 phase).

    We’re single phase at the moment. We were factoring in upgrading to 3-phase to get the best speed from the charger.

    It’s a three bedroom place, two adults, a/c, lots of working from home and gadgets drawing power.

    • Bigboomboom on 14/06/2023 - 12:13
      +1

      No need to upgrade to 3 phases, single phase 7kW is plenty fast enough. In order to support 11kW (can get up to 19kW if you buy Porsche Taycan but that's probably not bang for buck?) you would need really big solar unless you somehow has Summer all year. For instance my 10.5kW Q.Cells Q.Peak panels + 8kW Fronius inverter is giving me 10kWh daily right now in Winter (Western Sydney). In Summer it can go up to 60kWh per day but Winter is totally different story.

      I have 7kW ZJ Beny OCCP charger at home but can only use solar charging during weekends, when we take the RAV4 Hybrid and leave the Atto 3 at home. No battery because home battery prices still don't make economic sense yet.

  • JIMB0 on 14/06/2023 - 07:51

    The thing with batteries and heat pump hot water systems is are they going to last long enough to pay for themselves over their limited lifespan. The heat pump hot water systems don't have the best reputation for reliability.

    Next to consider is in winter you'll have far less solar generation and a higher demand from heating your house. You'll need to import power.

    How big of a solar system are you going to put in? Are you going to put panels on a south facing roof where the generation will be very little in winter?

  • lgacb08 on 14/06/2023 - 11:14

    You have given very vague information so won't have the best answer. How many people in the household, how much electricity you're using on average a month? How much money are you willing to spend? What's your house orientation and roof design like, is there any shading?
    Best general advice is to fit the most number of panels on your roof because it will be cheaper per kw and you'll find yourself using more electricity overtime. You don't need battery right now because there's little cost savings on it.
    As for hot water you'll need to spit out at least $4-5k to get heatpump, which will use a lot less electricity (8kwh a day) but if you can get 10kw or even 15kw solar you'll have crap load of excess electricity to divert to a traditional resistive tank (20kwh per day) which only cost you $1500 max and last for ages. And remember there's very high chance you will get down to nothing for export to the grid every year so within 5 years you can still be ahead money wise.
    having an electric car will help but how likely are you able to charge it during solar hour? The only thing to consider is upgrading your house to 3 phase so you can install larger solar system and 22kw charger if you ever need it but this set you back at least $2k.

    • bobbieb on 14/06/2023 - 19:31

      Ah… I'd kinda assumed that we could look at the tech/hardware side of what works well, without necessarily wading too deep into specifics, but here goes.

      How many people in the household, how much electricity you're using on average a month? How much money are you willing to spend? What's your house orientation and roof design like, is there any shading?

      • Household: 2 adults, 1 pre-teen.
      • Usage:
        • Electricity - 25kwh daily
        • Gas - 15MJ daily (hot water only)
      • Budget: Happy to pay for a good setup that will work the way we want, without going over the top expensive.
      • Orientation: House faces north east. No shading
        • There's potential to add some extra panels to our flat freestanding garage roof, but that gets a bit of shade from the neighbour's PITA tree. Maybe a small standalone setup for car charging, or is that being silly/wasteful?

      The only thing to consider is upgrading your house to 3 phase so you can install larger solar system and 22kw charger if you ever need it but this set you back at least $2k.

      Getting a 3 phase feed to the house has been on our todo list for a while for other reasons (having plenty of power for the treadmill and home office equipment), so we'd happily go the extra 2k if it ticks those boxes too.

      • lgacb08 on 15/06/2023 - 09:59
        +2

        Ok, so key question left was how much are you willing to spend. If I were in your shoe I'd look at getting three phase and largest system I can get on my roof (15kw or so). A 6kw system is around 6k give or take, but you probably only need to pay 2k extra to double it. With 10kw at least you can literally pump excess capacity into a cheap resistive hot water tank and get pay back within a year, doing so will help you getting rid of gas altogether. In summer you will have excess for ev car.
        A basic 6.6kw can be enough for your need if you go heatpump but that's at least $4k extra so expect to get at least 4-5 years to get ROI (but you don't have to go three phase for short-term gain).

  • dtc on 14/06/2023 - 11:20
    +1

    most solar installers will have programs that can map out all of the options for you ie install a certain capacity, look at your use, look at use and generation over different times of the year, attach a hot water system of a certain type and how that plays out, what happens if you attach some other product that draws power (ie an EV charger). They just plug it in and a report pops out - easier than you spending hours trying to figure it out yourself.

    Most of the time the issue is that you generate lots of power at times you dont use it (middle of the day) and the feed in tariffs arent as great. However if you can divert that power into (say) a hot water system which the holds the heat until you use the hot water at night or in the morning, then that is a good outcome (ie 'off peak' heating but not actually during off peak, which is generally overnight). This assumes your feed in tariff is lower than any grid consumption rate

    Total cost of ownership does suggest that a standard (rather than heat pump) HWS works out better.

  • EBG on 14/06/2023 - 13:03
    +1

    Realise you have done lots of research online already, but you might find The My Efficient Electric Home (MEEH) Facebook group is useful for some advice as they have extensive discussions on this stuff that may help you.

    • bobbieb on 14/06/2023 - 19:11

      Thanks, I'll check it out.

    • MikeKulls on 19/06/2023 - 21:23

      Just don't mention wood fires there :)

  • MikeKulls on 19/06/2023 - 21:23

    Don't get suckered into green tech misinformation. Here's my opinion on each
    - solar is a no brainer, get a big system
    - batteries are a complete waste of money and will never pay themselves off
    - heat pumps are only worth it if you are replacing the unit anyway. Their savings are proportional to usage so if you have low usage maybe not worth it. Also solar actually works against them mathematically, ie if you have solar the saving for a heat pump go down. There are some decent heat pumps in the range of $2500 that are pretty good and should pay themselves off.
    - EVs should only be purchased if you do a lot of Ks. If you don't use your car much it's actually better for your wallet and for the environment to let someone who does higher Ks buy it.

    • bobbieb on 20/06/2023 - 07:03
      +1
      • EVs should only be purchased if you do a lot of Ks. If you don't use your car much it's actually better for your wallet and for the environment to let someone who does higher Ks buy it.

      An interesting thought. I'd love to understand the math behind this.

      Between covid, WFH, and normal public transport usage - my Ks are on the super-low side. My current run-about is pushing 10 years and hasn't broken 30k yet.

      • MikeKulls on 21/06/2023 - 13:33
        +2

        I'd just keep your existing car. I could afford a new car but keeping my 2006 dual cab because it's never let me down and I really like having a car I don't have to care about. It opens up a lot of parking spaces. In my previous sports car I used to have to drive around looking for spots that suited my criteria, usually right down the bottom of the carpark. Now I'm happy to park 2cm from someone else if they are on the edge of the line for example.

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