gibbo9000

I haven't looked at Reposit lately but looked interesting a couple of years back, but they were a bit 'young' as a company and it was hard to get clear information on its capabilities. Hopefully that has improved. What I would look for in any truly 'smart' controller is something that looks at the local radiation forecast for the next day and and makes optimisation decisions based on that, particularly in a 2 tier tariff situations. Only that way can they effectively manage overnight charge levels depending on expected solar generation the next day. Some do that on a ' what we expect this time of the year' basis but that is not as efficient as actually reading something the solcast.com.au forecast. Gibbo

Totally agree. I would go further and suggest the subsidy could be moved from panels / inverters towards batteries, and the power distribution companies should chip in as well. Whilst panel / inverter subsidies have been great, we are at the point where underlying costs make them a sensible investment decision without subsidies. And if the distribution companies continue to struggle (and not invest) in a network that that will embrace distributed generation, subsidise batteries to help maintain balance onthe use of the grid.

Interesting and thought provoking analysis Jason. Need to think about for a while and apply it to my situation and see where it comes out. That peak rate looks high relative to Vic. We are in suburban Melbourne and more like peak 37c off-peak 22c and FIT 12c. My two immediate observations: Wonder if there is any evidence on Warranted versus Actual life for a battery - and whether depth of cycles matters. Agree it should be in the analysis though. I agree with the 'solar isn't free' argument - but for two reasons. The first is the opportunity cost of the FIT as you say. The other implication of free is the capital cost of the system is written off as a sunk cost (a decision you have made and can't reverse - so shouldn't influence future decisions). Not sure whether that is wrong or right in pure economics, but doesn't sit well with me. I spent the money and am looking for return on Solar PV investment, and that is through a cost to its output. Gibbo

22 Panels totaling 5.4kW and Delta Solivia inverter dating back to 2012 and still going strong. Added Powerwall 2 in 2018 along with upgrading breakers on PV set up, and rewiring and separating internal switchboard into a main and sub board to separate out the essential circuits (backed up by Powerwall) from the rest. Best advice the sparky's ever gave us was to install an MDF panel on some 2 x 4 timber behind the Powerwall / Inverter etc. to hide all the wiring. The Powerall is an AC connected system that sits on the house side of the Solar PV inverter, and comprises the battery and its own 5kW inverter (the grey box upper left on install). This allows it to back up the essential circuits in the house when the mains fails. Powerwall also has its own monitors etc. that sit in the switchboard and support comprehensive monitoring.

Good pick up. I hadn't seen this article. Makes the blood boil 🥵 This debate has been around in different forms for years - whether reductions in FIT's or potential charges, or ramping up the daily service charge so impact of FITs is less. And then there was the suggestion of gross metering rather than net. So you pay market rate for ALL electricity you consume (not just what you use after solar generation) and you get paid (or not) for everything you export). All mechanisms to rebalance tariffs at the expense of solar PV generators. The potential impact of of the growth in solar PV, or distributed generation from the grids perspective, has been known for years - along with the complication that a lot of this generation is in dormitory suburbs with limited weekday use. Other countries have invested and embraced this, so sad to see some in Australia apparently burying their heads and sanctioning the PV investors. Will certainly drive initiatives to opt out of the grid and leave the utilities with a stranded network ultimately reduced to supporting those who can't afford to opt out.

Good points, and well understood from someone who has had a few luxury cars over time. I should have prefaced better around the justification for main stream consumer roll out as a viable / affordable alternative to reasonably economical fossil fuel alternatives of the same 'style'. My argument is pretty basic and should add in servicing costs. I also understand a desire by power companies for more EVs that charge overnight to help with base load on the grid - and if so perhaps there is an argument for subsidies. From memory I think it may have been NZ that had government by EV vehicles into their fleet, and then sell them into the consumer market relatively quickly as a way of reducing / subsidising cost to consumer. We have an 8 year old Prius V and the economics to change to a new EV are hard to justify while it is still going strong.

I am not sure I have ever read a compelling comparison of EV running cost versus fossil fuel. I have pondered the maths a few times and never quite get there - did I miss something? If I consider a Hyundai Kona it has a 64kWh battery that at, say, 25c/kWH costs $16 a charge. It does around 400 km on that - so around $400 per 10,000km. The petrol Kona does around 7 litres / 100km which costs around $10. So that is going to be $1,000 per 10,000km. The petrol Elite costs around $35k and the EV one around $65k. I gotta do a lotta km to make that math work? I know there are other reasons to own one, but that is still a massive gap.

This calculator may help you get a handle on what you could generate. https://solcast.com/rooftop-solar/free-pv-system-performance-estimation-tool/ Quite a useful site overall. One of the ones a few people use to get solar forecasts for the next day to help manage batteries. The thing to be careful of here is the maximum charge / discharge rate of the battery. The smaller batteries (1 - 2 kWH) are good for time shifting during the day (lots of small periods of storing / discharging) but not great for backup as their discharge rates are limited to max 1 - 2 amps, not enough to power a house. There can also be a fair bit of rewiring of switchboard to separate out the backed up circuits.

Lots of good ideas above. Another option for making sure it is not something like a highly inefficient fridge (or other appliance) is to grab one of these simple power meters that you can plug into the supply to any appliance and it will tell you watts / amps etc. About $20 at your local hardware store.

I thought I would share some experience on battery performance in what is probably a typical installation in suburban Melbourne. We have a 5.4kW PV system installed in 2012 with Tesla Powerwall (13.2kW storage) from 2018. My view is PV systems well and truly pay for themselves, but batteries not so - so maybe they have to go in the hobby or feel good camp. We are on a two tier tariff and our numbers show pretty consistent $150 a quarter saving across the year on top of the PV system - so roughly a 20 year payback ($600 a year on $12k for battery), which is likely well beyond the expected cycle life of the battery -- but who really knows. And to realise that level of saving we had to apply some smarts that don't appear very common amongst most of the battery installers we talked to. Fortunately the fact our house is on two phases confused many installers at the time and that led us to a couple of the smarter ones. But what interests me most now, and I wish I had known at the time, was the impact a battery has on our 'footprint' on the grid if managed well. Below are some pairs of graphs across the extremes of Melbourne. The first in each set is the basic solar generation versus house usage (instantaneous and cumulative) and the second is the battery view (so instantaneous Grid Use and Generation along with Battery Charge and flow). Let's start with a good summer day. On the first graph, strong solar generation between 8:00am and 6:00pm covering all the load (the heavy day loads are mainly swimming pool pumps) and a close to 15kW surplus of generation over need. On the second graph the battery started the day (midnight) around 60% charged (the red line. scale to the right), powered the house until 8:00am when the solar kicked in to carry house load and recharge the battery. Around 1pm the battery is full and excess is exported until 6pm when the battery takes over again and is back around 60% by midnight. So nothing drawn from grid, and export through the peak afternoon period when power is scarcer. The clear saving for us is not buying electricity at all, plus the feed in tariff. At the other end you have a bad winter day. From the standard graph our generation is well under house load for the day, even with pool pumps turned well down (and gas heating). The battery pattern here is quite different - it charges off-peak to 100% overnight, carries the morning load. marshals what solar it can during the middle of the day and powers the house through to off-peak time again when it starts charging for the next day. That is what locks in the winter gains. The smarts to do this should be included with all battery systems - it just requires a look at the predicted cloud cover or solar radiation for the next day to make a charging decision. There are some that do this, but in our experience beyond the skills of most we spoke to. And yes, some argue we are killing the battery with extra cycling - we will find out sometime. There are many variations between the two extremes that basically target a mix what morning charge should we target, and should swimming pool pumps run (along with judgement on washing machine, dishwasher etc.) Anyway, some food for thought. It fundamentally changes our footprint on the grid in a way that I sense is quite beneficial to an aging set of poles and wires - not driving large swings in export / import incessantly during the day as sun / clouds move in and out, using base load night time power, and not contributing to the peak in 'distributed generation' through the mornings in summer. Gibbo

There are a few gems out there, but unfortunately not the mainstream guys. Hopefully this forum will surface some of our joint experiences and help mobilise what I am sure is a wealth of personal knowledge on more linformed ideas and solutions. I went through many iterations of clamps and monitoring with solar alone (as Solivia Inverter had none) feeding PV Output. Looked at Reposit Power and others after that, but Powerwall (and complete rewiring of fuse box) streamlines things. The battery challenge for those on two tier tariffs like us is using the cloud forecast to determine optimal charge overnight. More on that in other discussions.

Fellow SNA'r with an interest. Well done Marc. Solar panels since 2012; Powerwall since 2018. Remain amazed at lack of smarts in optimisation of effective battery usage by installers. Deployed effectively the impact on the grid is very positive IMHO, and should be the focus of subsidies. Gibbo