Best Way Forward

[Karasun]

Hi all, looking at doing something about the solar at my place in 2026. Buying at about .48c / kWh and selling to grid at just .03c / kWh. Hoping at getting some solar tips and tradie/company recommendations? Bit of info: I'm in the Fleurieu Peninsula (SA). I've only got a 2.5 KW system and its about 13 years old, however it produced about two thirds of what was used in the last quarter so I guess its useful (used 864 kWh and sold 633 kWh to grid). I use about 10 kWh / day, and on the Energy Australia Flexi-Plan (get $75 cr / quarter via Australian Gov Energy Bill Relief). The house runs only on electricity and I use a normal 315L outside electric hot water cylinder. Also, there is empty space on the roof and it is not shaded. Interested in best value dollar for dollar solution/s, not just necessarily chucking everything out and buying a new squillion dollar system, although obviously happy to replace components that are no longer functional. From what I can see there are lots of clever tricks and options out there from solar power diverters, fancy new panels, clever hot water systems, and of course battery solutions. I'm open minded and just looking for ideas atm, especially innovative budget friendly ideas. Any information/tips appeciated. Thanks for your time.

[Liam]

With that buy/sell price gap, the biggest wins usually come from boosting self-consumption rather than exporting, things like adding panels, load shifting, or using a solar diverter for hot water. If your inverter’s still OK, upgrading in stages (panels or hot water first, small battery later) is often the best value.

[Karasun]

Thanks Liam, sounds like a great idea....

[Karasun]

actually trying to understand diverters a bit more...
if the hot water cylender only powers up via panels between 10am and 4pm, does the hot water stay hot enough to use outside those hours (eg night/early morning etc).
...also will power still go to the grid after the cylinder has heated up?.....in other words....is the 315L cylinder big, or hungry enough, to suck up all the power produced between 10 and 4? if not, then I guess i'm back to square one because i'm just selling back to the grid again (the excess) at only .03 / kWh.
this aside, can anyone recommend a reasonable installer and/or inverter?

[Liam]

Generally, if a 315-liter water tank is fully heated during the day, and with good insulation, the hot water can usually meet the needs for nighttime and early morning use. Many households already achieve this through off-peak hours or solar water heating.

Once the tank reaches the set temperature, the splitter usually stops supplying power to the hot water system, and the remaining solar energy is fed back into the grid as usual. While a 315-liter tank can absorb a considerable amount of energy, on sunny days it often cannot consume all the electricity generated between 10 am and 4 pm, so a certain percentage of electricity fed back is almost unavoidable.

However, in practical terms, at least you are converting some of the almost worthless electricity fed back into hot water that would otherwise be purchased at retail price, which significantly helps improve self-consumption.

Have you ever used a home energy storage battery? . I feel that using it in conjunction with a splitter might better cover evening and nighttime electricity usage

[Karasun]

great info Liam - thanks. it sounds like an diverter would certainly be helpful in terms of self-consumption. and while useful, it sounds like this scenario would still mean selling back to the grid at some point even in spite of our best attempts to use power between 10am and 4pm. the other issue that has crossed my mind is that this upgrade could be become obsolete when I eventually upgrade to a more efficient/modern hot water system after the current hot water cylinder dies, and if the diverter continues to be useful under the new system whatever it may be. as you raised though, i cant help but feel that I should be looking at what alot of people are doing I guess, which is the battery option. the question is where to start. its seems quite complex, and i have so many questions. for instance, I've been reading about this thing called 'AC coupling', and wondering if that would be a cost effective solution? if it were a simple case of just adding a battery and maybe a few panels to beef up the system, and claiming the rebate, that might put a significant dent in our bill with minimal capital outlay. it seems like a simple solution. I also like it because I get to use the existing system. sure its old and small, 13 years and 2.5 kWh, but as I said in my original post it neverthless produced two thirds of the power that we used according to our last quarterly bill (we used about 860 kWh and sold back about 650 kWh). going down this AC coupling option sounds interesting, but I don't really know the 'ins and outs' or detail involved - for instance would there be more to it than just adding a battery and some panels. having said that, if sticking with the old system presents more trouble than its worth in terms of future proofing, then I would consider alternatives.

[solar pete]

Hi Karasun,

To me you have a few options, if your buying on average 10kW/hrs. per day at .48cents per kW/hr your yearly spend is just under $2K per year then a small battery may be the best option, the other way to look at it is your system is 13 years old and although panels will last 20 years plus they do degrade overtime BUT inverters don't last forever, I would be inclined to replace the whole system with say a 6kW solar and 10 to 15kW/hr battery, typically adding about 6kW of solar panels when your doing the battery anyway adds about $3K to the cost of the job.

Full disclosure, I work for a solar company in Adelaide, cheers

[Karasun]

appreciate the input Solar pete,

yes spot on. we pay about that per year in bills.

unfortunately you lost me after 'battery may be the best option'....wondering if u could pls clarify the pros/cons as it all sounds very interesting..

so ur thinking I could go the 'AC coupling' route but ur leaning towards replacing whole system..?

[solar pete]

Hi Karasun,

Yeah you have very old solar panel's and even though they will work for 20 years the cabling and the MC4 connectors (wires and connectors on the back of the panels) get old and brittle and are very difficult, sometimes they fall apart in your hands, so no solar company wants to touch old panels unless they are removing them to put up new ones.

Often people really don't like to hear that BUT its the truth, and why most solar companies wont play with old panels, so if adding a battery it will most likely need to be AC coupled, and well any power you currently are using at night time can be sorted by the battery, hope that helps, cheers

[Liam]

great info Liam - thanks. it sounds like an diverter would certainly be helpful in terms of self-consumption. and while useful, it sounds like this scenario would still mean selling back to the grid at some point even in spite of our best attempts to use power between 10am and 4pm. the other issue that has crossed my mind is that this upgrade could be become obsolete when I eventually upgrade to a more efficient/modern hot water system after the current hot water cylinder dies, and if the diverter continues to be useful under the new system whatever it may be. as you raised though, i cant help but feel that I should be looking at what alot of people are doing I guess, which is the battery option. the question is where to start. its seems quite complex, and i have so many questions. for instance, I've been reading about this thing called 'AC coupling', and wondering if that would be a cost effective solution? if it were a simple case of just adding a battery and maybe a few panels to beef up the system, and claiming the rebate, that might put a significant dent in our bill with minimal capital outlay. it seems like a simple solution. I also like it because I get to use the existing system. sure its old and small, 13 years and 2.5 kWh, but as I said in my original post it neverthless produced two thirds of the power that we used according to our last quarterly bill (we used about 860 kWh and sold back about 650 kWh). going down this AC coupling option sounds interesting, but I don't really know the 'ins and outs' or detail involved - for instance would there be more to it than just adding a battery and some panels. having said that, if sticking with the old system presents more trouble than its worth in terms of future proofing, then I would consider alternatives.

Yes, regarding the AC coupling function you mentioned, some inverters have built-in coupling capabilities. An efficient approach is to utilize AC coupling technology. This means you can choose a hybrid inverter with built-in AC coupling and then directly pair it with a battery storage system.
This fully utilizes existing equipment and offers great flexibility for expansion. How can I explain this to you? For an explanation of home energy storage batteries, you can refer to this link: https://cmxbattery.com/product/48v-7...nergy-storage/ It seems this website also offers inverters with built-in coupling capabilities. Look for them yourself; their specifications might perfectly match your needs.

[Karasun]

thanks for ur input and assistance Liam and Solar pete...AC coupling or new system ?....sounds like each has pros and cons...plenty to think about. wondering if you guys can recommend good/reputable installers or companies that will service Fleurieu Peninsula in SA...?

[Liam]

thanks for ur input and assistance Liam and Solar pete...AC coupling or new system ?....sounds like each has pros and cons...plenty to think about. wondering if you guys can recommend good/reputable installers or companies that will service Fleurieu Peninsula in SA...?

Yes, AC-coupled systems and brand-new photovoltaic systems each have their advantages and disadvantages (for example, AC-coupled systems are more suitable for expanding existing photovoltaic systems with energy storage, while brand-new systems offer greater design flexibility). The choice depends on your roof, electricity usage habits, and budget. Regarding local installers, I'm not very familiar with them; I suggest you consult people who have already installed solar power, as they might be more helpful.

[HernyPerks]

I’d look at replacing the old 2.5 kW system with a bigger setup and maybe a battery, since your buyback is tiny. Local installers around Fleurieu Peninsula can size everything properly.