• Richard Davies

    Really detailed info here, thanks for that.
    Obviously for avoiding load-shedding this is great… would love to see more of the financials (i.e. is it worth it?)

    • 小杜

      Electricity isn’t going to get cheaper, so if you can mitigate the costs of it now, year on year you’re winning.

      Thats my point of view really, as I’ve said many times on MyBB and on here in a few posts.
      Obviously I imported my panels and inverter, and setup the system myself, so my costs are quite close to import pricing, but its still extremely worth it regardless.

      I’m about to start building a new house on a plot I just bought, so will be putting a larger system in next year. If I didn’t think it was worth it, I wouldn’t bother!

      • Richard Davies

        I see lots of people making that call — but it is possible to get the HARD financial facts on it…
        Basically if you spend R50,000 on a big system, you’d better be making 6% per year on it, or you’d be better off just putting into savings bonds and just paying for the electricity.
        I can do the numbers, I’ll put it up on blog.homebug.co.za

        • 小杜

          I have put numbers up in the other posts, but I’ll give you a rundown below:

          Our electric bill was about R1000 a month in 2012 for our 3 bedroom house.

          I replaced the house geyser with 2 x 150L solar hot water geysers in series, which brought that down to about R650-700 a month.

          I replaced all the lights in the house with LED’s in 2012 too (mostly 3W bulbs). Lighting doesn’t really chew much electricity in our house though, although everything helps!

          Our main culprits for power are the Fridge and the Freezer (constant load’s), washing machine and dishwasher, then cooking. We don’t use the kettle much, or cook nightly, so thats less than usual households.

          A 2012 electric bill R650-700 = R1000 now in current pricing. Winter would have been more usage for heating, I don’t have records for that to hand though.

          Right now the bill is about R150-200 in winter, summer R0 – R5.

          We’re firmly in the lower tariff monthly (<600KW a month usage).

          We're saving about R12,000 a year at current 2014 pricing (R1.53/KW in Cape Town). Next year we'll be saving close to R14,000 (assuming 15% increase). The year after we'll be saving close to R16,000…

          If that trend continues, our "payback" time will be 5 years using a fairly simplistic method below:

          R80,000 sunk cost for system.

          – Inverter cost me RMB12,000 (R20,000)
          – We have 16x300w panels on the roof @ RMB850 a panel (R1600 a panel).

          – Mounting and cabling was about US$500 (R5000).

          – Installation was free (did it ourselves).

          – Electrician to sign off and run cabling to DB Panel was about R1000.

          Y1 R12,000
          Y2 R13,800 @ 15% yearly increase
          Y3 R15,870 @ 15% yearly increase
          Y4 R18,250 @ 15% yearly increase
          Y5 R20,100

          = R80,020 saved @ 15% increase a year in Eskom pricing.

          Its not accurate, but for a rough guesstimate, shows that its worthwhile installing panels, especially over the life of the system.

          Panels should last 15-20 years+, and the Inverter 10-15 years.

          Typically people replace panels not because they're dead, but because newer panels give higher Watt output than the old ones. I should be ok for that, as I have fairly acceptable sized output already.

          Electricity pricing is forever going up, not down, so each year it increases, my return on investment increases too. Pricing looks to be increasing about 15% a year, year on year. Probably more if Eskom gets its way.

          While I'm not particularly worried about the system cost – it was more of a proof of concept/fun project for me, I'm quite happy that it works wonderfully, and the benefits are there for me, year on year..

          Its hard to cost it out properly as I brought in a container of panels + other items, but assuming I use a blanket price of 20k for whats installed for shipping + clearance + 14% vat it works out to about R80,000, which I've used above.

          I may go completely offgrid at some point – I've worked that out to be an additional R70,000 (3 x inverters @ 15,000 each + the rest in batteries).

          My costs are not necessarily something you can point at for the average system though. I have a 3 phase setup (which means inverter pricing is higher), and I deliberately went for grid tied, and I bought an inverter than can suit my future needs (a 10KW 3phase one). There are substantially cheaper single phase ones available. For my next install I'm probably going to do something similar, but it depends on whether I have 3 phase on the plot I just bought. I need to check that!



          • fp naude

            Hi Lawrence

            Please let me know where I can buy a Growatt 6000UE inverter?



          • 小杜 (xiao du)

            Suggest contact them directly. I usually deal with Ivan –
            Email: ivan@growatt.org Skype: ivan15019271958

    • Jonathan Parkinson

      I have been doing my own research, and at every turn there are those (boring) naysayers who try to give you every reason why not to use solar/inverters/batteries to circumnavigate Eskom. One such problem is the question of legality. I have been told that any system would have to have separate wiring, not even using the same conduits of the main household wiring! If you go ahead and use existing wiring/conduits, you cannot get a certificate of compliance – ergo you are not insured in the case of your house burning down! What do you know of this? It obviously adds even more cost to setting up an ‘off the grid’ or even back up system with an inverter and batteries.

  • Macafrican

    Why the complexity for hybrid? You live in Cape Town, there is local company MLT that ships hybrid systems for single phase and three phase. To my knowledge it handles what you are describing very easily.

    If your solar output exceeds your house loads, then excess solar goes into batteries till the batteries are full (they don’t draw current when they are full) then you output to grid, which can mean 10 different things in different meter situations.
    If you solar output is less than loads, it will use all the solar and the balance from grid or you can tell it to use solar plus first use batteries to a target discharge level.
    if grid is down you run off battery till batteries reach a discharge level then it can auto-start a gennie. How long you run battery is obviously function of how many Ah you have.

    All of this in one box and it is an SA product with lots of reference sites in the Cape

    This is what I understood from the literature anyway…

    • 小杜

      A number of reasons, really.

      Price would be the main one – MLT’s inverters are quite expensive compared to doing it the way described above. A similar specced inverter from them is about 120,000 last I looked. I can do that for about half.

      Secondly – they don’t have a product that really fits my needs – their lowest suitable three phase device is 18kw, thats rather overkill for my needs. ( http://www.mltdrives.com/datasheets/MLT%20PowerStar/PS-16-18kVA.pdf )

      Thirdly would be that the German guy there couldn’t be bothered when I visited them in Kenilworth, so didn’t really give my incentive to use their products. Pre-sales is important, especially when you’re dealing with end installs with 6 figures numbers.

      They were similarly not interested in selling product when I saw them again at the solar / green thing in Greenpoint park.

      The people at ExSolar in Somerset West on the other hand spent the time to go over options and were helpful.

      • Macafrican

        Thanks for prompt reply!

        R120,000 inverter???? That’s about what we paid for 70KW inverter when we went solar on our farm. Yes as in 300 solar panels. Somebody maybe misunderstood your question. Does ExSolar not do MLT kit?

        I am lucky my present council meter runs backward. Changes everything as I now only need to store energy for backup, not for time-shifting = lot less batteries.

        Yes three phase changes the numbers quite a bit – three inverters after all. I am presently on three phase municipal at a huge monthly cost, so even if I drop consumption from 1200 to 400 pm I will still pay R900 for the connection…. my first kWh costs R900, the second R450, etc

        So : I am firstly downgrading house from three phase to single phase, then I am rewiring the DB so that a bunch of non-essential / dirty / heavy loads don’t go via the hybrid at all. ie aircons and underfloor run council direct, not backed up, not solar powered That way the hybrid system can be a small (8KW) system and cope as UPS for all of my lights and plugs. I hardly ever need more than that, the system can double for short bursts, so I am not going to buy 18KW of inverters for maybe a day per year that by accident the pool pump and four aircon are on the same time. We have solar water + heat pump + gas kitchen and haven’t run underfloor for years.

        Then everything else in the house connected to much smaller hybrid from MLT. I think between about 4h of battery backup + 6KW panels + 8KW hybrid + installation it should come in at below R150,000. If it runs nicely I will add another 3KW solar on another side of house likely with own inverter, as the hybrid can take a second AC feed. I will never have gennie so the second lot of solar will pretend to be a gennie.

        I hear you on MLT customer service issues, but they have a lot of expertise. Other than my MLT preference, does it sound sensible?

        • 小杜

          Not sure why your underfloor isn’t running off of solar hot water heating – is it hydronics or electric? Solar hot water is a no brainer for underwater heating – I’m planning on doing that in my next place.

          Summer time you should be running cold water through the system to cool the house down.

          I’d suggest you look at insulating your residence better. If you need to run a/c its not very insulated… Much better off improving that and spending less on heating / cooling.

          Key to solar is to reduce the loads first, then get solar. Sounds like you’ve done that as best you can though. Without knowing what you use, its hard to guesstimate.

          Don’t forget for batteries, you’re looking at 30% of actual runtime vs capacity. eg, if you have 10 x 12v100Ah batteries for +-10,000Whr, you really can only use about 3000Whr of that.

          I had a Flukso ( http://www.flukso.net ) electricity monitoring system in place for a few months before I even bought anything, so I could monitor all our own house loads.

          I nominally have a 4kw system in panels at the moment, with 1x 10kw 3 phase grid tied inverter from Growatt. I should probably put more panels up, as I brought 30 over, and used 16 so far (they’re sitting in storage at the back of the house). I’ll most likely be ordering the 3 inverters I need (Victron Multiplus 3KW x 3) quite soon @ R14.1k+vat each + 10 x 12v@100A batteries @ 1000each, to give a rough 3KW @30% discharge system with losses etc. Will make sense for me to have more panels up for winter to cover cloudy days. Our lowest generation in winter is a handful of kw on rainy / cloudy days. I can supplement that with Eskom if need be though. Summer time we already generate way too much for our needs.

          I’ll be heading back to China again in September, so will be buying more panels, and another grid tied inverter there, plus hydronics bits and bobs, and windows+frames for my new house. Its amazing how much you can save if you shop and ship yourself!

          • Macafrican

            OK thanks, happy shopping!

      • Greg Lumley

        Funny you say this, it seems if you aren’t industrial they don’t care.