Five things I've learned about solar and storage

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It’s now been almost three months since I installed rooftop solar and battery storage on the 30-yar-old home I bought early last year, and there is absolutely no doubt it has made a huge difference to the nature of my bills, the source of my energy. and the way I use it.
As I wrote in October, I had 5kW of  LG 315 Neon2 solar modules installed – half facing east and half facing west, along with two 1.2kWh Enphase lithium ion battery storage units. Those $50/week bills are now a thing of the past, and I expect to pay no more than $50 a month essentially my network fee. The bills may turn out to be even lower.
Here are the five things I have learned about solar and storage:
Know your consumption:
It’s great to have an idea of how much electricity you use, and also when you use it. The quarterly bill only gives you a bulk reading that tells just a small part of the story. The real interest is in which appliances you use and when they are being used. The best way to do that is with a monitoring device. I used Solar Analytics, which are primarily for solar and storage monitoring but also give minute by minute usage data. They cost around $500 but may be worth it because it could deliver savings on what size system of solar and storage you choose.
Small is good for battery storage
I’ve only got two storage devices, and I could have installed more. But to what purpose? The 2.4kWh do not cover the oven or the kettle, for instance, but they keep most things in the house going for most of the evening, often powering the house until 2am or even 5am in the morning, and react quickly if household use jumps above solar supply during the day,
My daily draw down from the grid used to range from 15kWh to more than 30kWh. Now it ranges from around 0.2kWh to around 4kWh. The average since I replaced the electric hot water with an evacuated tube solar hot water system is just 2.2kWh.
As this graph below illustrates, I now use an average of just overt 8kWh a day from the solar array, and export around twice that much. 
That means that – courtesy of the 10c/kWh feed in tariff i get from community-owned and renewable energy focused Enova Energy (soon to rise to 12c/kW), I’m getting about $1.60 a day from solar exports, and paying around 60c/day from grid imports.
And I’m paying $1.50 a day for the use of the grid to buy and sell energy. that works out to be a net bill of around 50c/day – although I bet that rises in winter, as the days shorten and the solar production falls. So I’m figuring $1 a day on average.
Which is not to say that bigger batteries aren’t good. But right now, I don’t need one, and probably won’t unless I want to go off-grid, or provide back-up power in case of an outage. (Enphase won’t ride through a blackout, but the house came with a generator that I have yet to need).
Solar hot water is a must:
I chose evacuated tubes from Apricus for two reasons. One, they are local, two, they work, and three, I wanted to leave enough excess solar PV output to help fill my electric vehicle, if I ever get it.
This means that I went from this – the big block on the left is the electric hot water ….

two this …

There are a bunch of alternatives for electric hot water- using the excess solar PV f your electric tanks, using the various solar thermal offerings (such as fixed plate or evacuated tubes), or getting a heat pump, which also uses the sun. they are all better than using the grid (which basically means you are boiling the water twice – once in the coal plant, and another in your tank), and it’s good to know it will still deliver when the grid fails.
Battery storage prices are coming down:
Many installers report a lot of interest in battery storage, but not a lot of buying. That is starting to change, if the battery storage developers are to be believed, but it seems pretty clear the battery storage costs will come down quickly in the new year. Tesla’s Powerwall 2 effectively shaved 50 per cent off the costs per used kilowatt and that means that the combination of solar and storage can come pretty close, or even beat, grid power in most states. The Powerwall 2 won’t be delivered until February, March, so most competitors will hold their pricing levels until then.
Buy quality:
The price of rooftop solar panels are also coming down – thanks mostly to a big increase in Chinese manufacturing capacity that has not yet been matched by demand, and ever improving efficiencies. Offsetting this is the slight reduction in the upfront rebate – from 15 years “deemed”: output to 14 years – but the reality is the good quality solar modules can be bought and installed for less than $2/watt. Unfortunately, too many consumers in Australia are going for the “bucket shop” variety, installing the cheapest panels they can find. Avoid it. These are important pieces of equipment.
 

This post was published on December 21, 2016 10:56 am

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  • Will be great when a later version of Powerwall or an equivalent unit can direct DC direct from the panels to the Prius Prime or similar and thus conserve the home storage battery.
    https://www.cnet.com/roadshow/auto/2017-toyota-prius-prime/preview/
    Exciting times but not as exciting as they could be for the Prime Minister and the anthropogenic climate change deniers who lead him by the nose.
    Now we the Deputy Prime Minister telling the Prime Minister to support the financial parasite Adani, (and indirectly his close friend Rhinehart) :-
    http://www.abc.net.au/news/2016-12-21/adani-corporate-web-spreads-to-tax-havens/8135700
    Cayman Turnbull might be able to offer some advice to Adani re the Cayman Islands and what it has had to offer the Prime Minister of Australia in terms of tax avoidance.

  • "Solar hot water is a must:"
    Totally agree. It should be priority one for anyone North of Tasmania.
    We have 3 x flat panels that give us FREE hot water for 9 Months of the year.
    Evacuated Tubes would be even better.

  • "Solar hot water is a must:"
    Yup. We like our heat pump hot water that is switched by a timer. It can only switch on when the sun is up and (usually) driving the solar panels with power to spare. Solar hot water with no rooftop plumbing :)

  • re Apricus system - for the system to be truly effective, the detail is critical, for example, my system :
    High tubes to tank-volume ratio to suit Melbourne - 30 tubes and 250 litre tank
    4.8 kw Mid tank element, bottom inlet, top outlet, thermometers at top and bottom of tank and at tube manifold.
    If the tank is situated close to the tubes, then you can take advantage of smaller temperature differences between the tubes and the tank inlet (=cold water pipe) with very little pumping.
    The Programmable settings for the tank are important, using for example the Senztek SolaStat device, the close linkage of tank and tubes, and to suit 2 people showering first thing, a DW and a side loading WM which both heat their own water - so very little hot water use between early morning showers and the evening:
    (The SolaStat pre-set values are in brackets.)
    Temperature difference between tubes and tank inlet that will turn the pump on: 7 (12)'C
    Temperature difference between tubes and tank inlet that will turn the pump OFF: 3 (6)'C
    Tank temperature at which the element will automatically switch on: 28 (40)'C (perhaps should be a little higher- depends a little on the flexibility of the tempering valve.)
    Tank temperature at which the element will automatically STOP heating the tank: 40 (55)'C
    How long the timer will delay the element coming on to heat from 28 to 40'C: 18 hours (4) (allows waiting overnight and morning till sun is effective, because there is little use of hot water till evening. Pre-set of 4 hours is the most expensive pre-set, esp for households which are empty during the day -why use electricity to heat hot water at 9 or 10 am after the early morning showers have lowered the tank temperature?)
    Because my tank is stainless steel I could afford to raise the max temp in the tank to 83 (80)'C so I can store a little more energy.
    The biosafe (60'C) and frost settings I have not touched.
    Is a meter necessary to analyse usage? The retailer Powershop offer half hourly download to analyze electricity use - after logging in, go to Usage> Usage patterns.
    Some other retailers and utilities also offer data.
    However, Giles if you switch on the 4.8 kw hot water element in your Apricus system, and have less than that amount coming from the solar system, will you also be drawing electricity from the grid? Is there a way the solar electricity can be diverted to the HWS element without dragging in the grid electricity?

    • Hello Ray, How many days of the year do you need to boost there in Melbourne and for how long each time? I'm interested how it performs in winter especially!

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