My first weeks with rooftop solar and battery storage

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A little over six months after I moved into a new home I have installed a combination of rooftop solar and battery storage. It’s amazing what a little bit of storage can achieve.

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One Step Off The Grid

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That’s the east facing array – 2.5kW in just eight modules.

Finally, a little over six months after I moved into a home (not newly built, just newly bought), I have – for the first time – a combination of rooftop solar and battery storage.

It’s exciting. So much so that I spent most of the October long weekend staring at the monitoring devices noting the amount of solar produced and what the batteries were doing, and offering advice about when everyone should take showers, switch on lights or operate appliances.

I’m told I’ll get over that soon. But here are a few thoughts about the first two weeks. I’ll write some more as time goes on and I understand the systems better.

As I wrote before, my previous house in Sydney may have felt something like a wooden tent, but it didn’t consume a lot of electricity (mostly because it wasn’t used for heating or hot water).

This new house, in the northern rivers of NSW, is an electric utility’s wet dream – electric hot water provided by the equivalent of an old kettle that keeps the coal-fired power stations busy at night, and daily usage of at least 15kWh for two and up to 30kWh a day with visitors.

That was until a few weeks ago.

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The two Enphase batteries weight about 25kg each and fit easily on a wall in the garage.

That was when 5kW of LG 315 Neon2 panels were installed (8 panels or 2.5kW facing east, pictured above, and another eight panels or 2.5kW facing west – I don’t have much north roof space), and two of the newly launched Enphase AC battery storage systems (pictured left).

Why go for these brands? Well, frankly, it’s because I got a good deal (thanks to my friend Nigel Morris at RoofJuice).

But I do know they are both top of the range. And quality, for assets that will sit in the garage for 10 years and on the roof for several decades, is important. It would have been possible to get cheaper modules, and cheaper batteries. But the question is, would they last?

I like the idea that the new LG panels (315 watts) are powerful enough to mean they don’t actually take up much roof-space, and if I want to expand – to go off grid some time down the track or power an electric vehicle – then there will be no problem. (LG solar panels are heading towards 360 watts and then maybe even 400 watts).

I chose Enphase micro-inverters: First, because of the quality – I have heard too many horror stories about cheap inverters packing up after a few years and no one around to take responsibility. Also, because I get a little shade from gum trees east and west, particularly in the morning and late afternoon, this helps optimise the PV system’s output.

For the batteries, well, I’m kind of intrigued. There are a lot of offerings out there that seem good quality, but some of them are serious chunks of money ($10,000 or more). I liked the idea of a modular system where I can start small, get to know my solar production and consumption habits, learn what battery storage can do, and then see if I want or need to add more.

I already had a pretty good idea of what my consumption looked like, thanks to the monitoring device I got through Solar Analytics. It is still surprising that so many households have no idea how much various devices consume, or how their solar systems are performing.

Even before I got the solar on the roof, I learned a lot about my consumption patterns, and the power needs of the various appliances, including the giant kettle that passes for a hot water service, the real kettle for hot water, the electric oven (we have no reticulated gas up here), the pool pumps and the water pumps (we have no mains water either), and the septic system (we are off grid for that too).

This is what a really ugly day looked like before solar and storage. Check out that hot water on the left. Total consumption that day was more than 25kWh (though some days went beyond 30kWh), total consumption for the week was 150kWh, and a bill just shy of $50/week, heading for $2,500 a year. Ouch.

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So, what have I learned in the first weeks of my solar and storage? First of all, solar is around one third of the the price of grid-based power. I produce it and it’s clean. I haven’t crunched the numbers on the storage yet, but when I’m paying 34c/kWh for grid power, and many others are paying twice that amount, there’s a fair bit of room to play with.

All up, on a fine sunny day I am producing more than 30kWh, and that will rise into summer. On a really cloudy day, I am still generating around 9-10kWh. Even on a rainy day, the LG panels and Enphase micro-inverters are still good to generate around 6kWh.

The battery storage – even two small 1.2kWh units like the Enphase ones – are keeping my house powered through to past midnight if they finish the day fully charged, and even up to 6am on one occasion.

(That is with the exception of the real kettle and the electric oven, which cause spikes in consumption not met by the storage. But hey, I’m paying $500 a year for access to the grid, so I might as well use it).

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The Enphase batteries don’t take a lot to fill, and they charge and discharge at a maximum of 270 watts each. That gets dissed in some quarters as being not enough.

But with two units, 540watts is enough for lighting and TV etc. When I take out the electric hot water, my consumption will likely be all but invisible to the grid on most days, but for the kettle and the electric oven, and random visitors with hair-dryers.

Yes, I could capture more solar and put in a bigger box for later use, and I might just do that, by adding another one or two units. But I will check out the usage over the seasons before doing so.

But it underlines the attraction of a modular storage system, remembering that according to some analysts it is the first kilowatt hours of storage that are the most valuable. (And, according to installers Tim Hodgson and Mark Hickey from Light Touch Electrical, it was the easiest battery storage installation they had done to date. And they have done a few. It was, they said,  almost literally, plug and play.

Even with this amount of storage (and of course this amount of solar) I’m expecting my bills to all but disappear, but for the fixed network charges, which in this part of NSW are a whopping $1.50 a day! That’s $500 a year. As I learn more, I will get a better fix on my return on investment.

screen-shot-2016-10-18-at-10-57-38-amThe Enphase system also comes with its own monitoring device and displays, called Enlighten, which indicate performance of each panel, and the state of charge for each battery. I think this is absolutely crucial – I see so many people with solar who have absolutely no idea how their equipment is performing.

I will go into this further at a later date, but here is taster of what you can see (to the left). It’s taken at 10pm, over a quarter hour period.

So what are my overall reflections at the end of the first weeks?

I wish I had done it quicker – it would have saved me around $40/week. I suspect my power bill, particularly in summer months, will fall to around zero. Yet to see for winter.

Even with a small amount of battery capacity, I am almost invisible to the grid, at least for consumption. I’m paying a hefty fee ($500 a year) to basically use the grid as a bigger-back up battery, and to export my excess solar.

In 10 years time, with the cost of storage going down significantly, and the cost of solar also falling, the network is going to have to make a compelling offer to compete with these technologies. Fortunately, the local council here appears serious about the concept of developing micro-grids and sharing energy.

Like most people, I like the idea of an electric car, when they come down in price. This solar, which is going to last for at least 25 years, will be able to provide much of the power to charge those batteries.

This article was originally published on RenewEconomy sister site One Step Off The Grid. To sign up for the weekly newsletter, click here.  

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38 Comments
  1. trackdaze 3 years ago

    Trouble finding your exports?
    Any chance of shifting more of your hot water heating to solar seeing the batteries fill up quick?

    • Giles 3 years ago

      Ah ha. Actually, the hot water has gone. Could have done a PV diverter, but decided to go solar hot water as got other plans for solar output. Total Grid consumption today? 0.4kWh!

      • Giles 3 years ago

        p.s. the solar hot water only installed yesterday after this article finished.

        • trackdaze 3 years ago

          Thanks.

          Looks like your batteries are charged by 1pm.
          So there ought to be exports afterwards with production higher than consumption?

          • Giles 3 years ago

            All the yellow bits are exports!

          • Peter G 3 years ago

            Hi Giles, The evacuated tube HWS are great, but I don’t know if you haven’t given the kettle HWS a bad wrap.
            As a sunk cost, redesigning could be economically efficient even if not thermally so, especially when PV is so cheap and you have the roofspace.

            Installation costs vary but $40 will get a replacement 2.4kW or 1.8kW lower HWS
            element (to fit under your PV generation profile) and a $10 timer can approximate the export profile (not as good but much cheaper than a commercial diverter).

      • Tim Forcey 3 years ago

        Well done Giles. So you have opted for solar thermal rooftop hot water (electric boost I presume) and not heat pump? It will be interesting to see how much boosting electricity your hot water system requires in the dead of winter. Of course I am thinking heat pump is the better option these days, in most climate zones. The Sanden brand hot water heat pump (with CO2 refrigerant) would be expected to power along in winter quite easily, consuming some electricity but not heaps.

        • Giles 3 years ago

          hi tim. yeah, i had solar thermal on a house i rented up here last year and didn’t have any issues, and this is better quality – evacuated tubes. so it will be interesting to see.heat pumps getting mixed reviews up here – are they ok in warm climes? some say better in milder ones

          • Brian Bartlett 3 years ago

            G’day Giles. My heatpump performance right on the Tropic is averaging less than 1.5kWh/day through winter. This is for 2 people. At less than half the quoted price of a solar thermal to install it seems to work well with no problems during wet or cold weather. And so easy to install as a ‘bolt on’ replacement for existing electric storage systems. As you have discovered solar is the best teacher as it makes people interested in their energy use, often for the first time, to see if their ‘investment’ really does pay off. It is equaled only by good live energy monitoring and subsequent data evaluation. Great feedback on the battery system. My calcs have also arrived at around 2.5kWh storage capacity being a good starting point btw.

          • Steve 3 years ago

            What brand of heat pump do you have? I’ve heard mixed reviews and positive reviews seem to be highly brand specific

          • Brian Bartlett 3 years ago

            I am using a Quantum 150L AC6 series. It is my 2nd heatpump from this source. If you check out a detailed reply I made on this link with respect to my heatpump experiences you should get a bit of an idea of reliability and potential problems. My reasoning in going for the smaller heat pump was less people, less daily system losses, lower cost and easy installation. It was done in under 2 hours including upgrading pipe insulation and new temp valves. https://reneweconomy.com.au/2016/agl-to-offer-1-a-day-all-you-can-eat-electric-vehicle-charging-62209

          • Steve 3 years ago

            Cheers, thanks. Some pretty hectic comments on that hread! How much was your Quantum unit? Is that the $2k you mention in the other thread?

          • Jonathan Prendergast 3 years ago

            I got a heat pump in Sydney last year, a Siddons bolt on. It reduced my hot water production energy use from 8kWh per day to 2kWh per day. It was a net cost of around $2,000 (after STCs) and saves us around $550 per annum. We love it. We are arranging rooftop PV at the moment, so will switch it be powered by our PV to ensure more self consumption.

          • Tim Forcey 3 years ago

            Heat pumps move heat from a cold place to a warm place. If the cold place is not that cold, they work very well! So yeah, heat pumps work more efficiently (more cheaply) in warmer climates than in colder ones. Nevertheless, the Sanden hot water heat pump is rated down to -10 C. So they can heat water even if the ambient air is below freezing (they are used extensively in Japan after all). Heaps of positive user experiences discussed at “My Efficient Electric Home” on Facebook. Generally Australian climates are ideal for heat pumps. I think the automobile got “mixed reviews” in the early stages…

  2. Tim Forcey 3 years ago

    Folks are welcome to further discuss their (actual or aspirational) Efficient Electric Homes at the Facebook discussion group “My Efficient Electric Home”! https://www.facebook.com/groups/996387660405677/

  3. handbaskets'r'us 3 years ago

    Just thought I’d mention, although you can only have 5kW inverter capacity, I’ve put 6kW of panels up there. This overclocks my inverters a bit, but no probs in 5 years and another 18% or so power output. Most inverters are rated +or- 20% or so…
    That would knock out that pesky and psychologically significant 0.4kWh.

  4. Darryn McKay 3 years ago

    Great write up – how much approx were the batteries to install?

    • Giles 3 years ago

      won’t tell you my price – but i think less than $4,000 for both is standard. installation was part of solar installation so not sure what bit where batteries, but it didn’t take them a long time. all done by lunchtime by one guy while the others did the solar (racks and some electrics put in a week earlier)

  5. Rod 3 years ago

    “I’m told I’ll get over that soon” LOL Nope, I’ve been taking weekly and Monthly readings and filling in my spreadsheet since installing my 1st array in 2001.
    It is a sickness.

    • Giles 3 years ago

      i suspect you right, but i won’t view it as a sickness!

    • Ant.. 3 years ago

      I started analysing months, then fortnights then weeks now I am down to days seriously considering hours or I might jump that and go to 15 minute time slices.

      • Rod 3 years ago

        Why stop there? My new AGL smart meter has 5 minute signals which can be downloaded in CSV format. I’m not that keen though.
        My most useful tool is my Wattson whole house live monitor.

          • Rod 3 years ago

            Is that your table or something provided by your retailer/inverter?
            Who wouldn’t like ROI of over 12%?

          • Ant.. 3 years ago

            It’s an automated financial model which I have built using the ‘Numbers’ spreadsheet application V4 [Apple OS X Sierra]. I have created a data based that contains our monthly performance records starting from 1-31 July 2015. Based on user input the model will automatically calculate any period including a Quarterly Forecast [using current or historical data dependant on past or future months], Monthly, Quarterly, and Annualised periods. The yellow flags indicate that the label to its immediate right has an active mouse over comment. I have not built the model to calculate an exact billing cycle which in our case usually starts on the 20th of the month for 90 days. For simplicity the model calculates from the first day date to the end day date in any month. The following is a typical analysis using our system performance. Return on investment ROI is the tax free savings divided by the cost to get in which includes both the PV and Storage. We have a plan to increase our storage to 4.8 kWH. So far on average with one 1.2kW storage battery we are getting 1.022 kWH per day. October 2016 will be the first month that we have a full months data.

            https://uploads.disquscdn.com/images/dcd88584bd0e5d79311ee7998ef5c081d15b5e4286d23556412e7b904fb6d70f.png

          • Rod 3 years ago

            Nice and plenty of information there.

  6. Ren Stimpy 3 years ago

    Couple of good insights there. One of the things that stands out to me is that a 5kW system can now be 16 panels down from 20, and say the panel output does get to 400 watts which is probably inevitable and then some, a 5kW system will then be just 12 panels. The pace of advancement in this tech is incredible, it’s got disruption written all over it.

  7. Ian 3 years ago

    Giles, you haven’t mentioned using heat pumps for hot water or reverse cycle air conditioning or retro fitting insulation in ceilings, walls etc. obviously the payback time for each of these measures needs to be calculated. I don’t like that huge chunk of blue at 2 am, presumably that’s the hot water heater operating in the night, maybe on an off peak tariff? You could use excess solar generated in the day, diverted to a hot water heat pump or solar thermal panels on the roof to get rid of that nasty grid load.

    If you speak nicely to Tesla, maybe they will give you an EV to test and write about as part of your personal off grid renewables experience;)

    Oops, didn’t read the other comments, you mentioned a swimming pool. Have you considered using solar for pool filtration? That is also a horrendous load. Roughly 1KW for 4 hours a day.

  8. Webber Depor 3 years ago

    much ado but no price == useless

  9. Alex Peterson 3 years ago

    Giles your article prompted me to take a close look at my P.V.performance for the last 12 months. Ihave a 4.5kw Rooftop system and have been changing my house, new A/C, new fridge, ceiling insulation replace many light with LEDs . The Solar PV has reduced my energy bill from $ 2,000 to $755 PA. As a daily average I export 12kwh and import 13kwh. I do not intend installing a battery as the RoI swould be low ie spending$10,000 to save $755 PA. My inverter is rated at 5kw so I will get a quote for some more panels.

  10. Mark Roest 3 years ago

    Giles, you said ‘But hey, I’m paying $500 a year for access to the grid, so I might as well use it).’

    I have a couple of questions.
    1. What’s your weather like in terms of solar interruptions? How many kWh would you need to weather a worst-case weather event if you quit the grid altogether? I’m assuming you replace the water heater with a really efficient one, perhaps solar if the economics work for you. Also, your solar person was really supposed to have you become as efficient as possible before calculating the needed solar. But you can still do this when you get your BEV. I also assume you are willing to hunker down a bit during long storms (or brush fires) to reduce the cost for a stand-alone system.

    2. If you couple the access charge with all the other charges, how long would it take for additional panels plus all the batteries you need to get to payback, if the batteries themselves are $100 per kWh capacity?
    3. Do you know any qualified investor who would like to (financially) help bring this to fruition over the next year, instead of 10 years? It looks like Australia is going to be a hot market!

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