Hi Karin
That’s a good question, and can be roughly answered with a few calculations. You’ll need to know how much you will get paid for the solar you export. You’ll find a link under “Feed-in tariffs” in this article:
https://forum.cleanenergyreviews.info/t/ch-8-what-financial-incentives-are-available/161
You can see general calculations for solar generation in NSW here. A conservative estimate is that you’ll generate 4kWh for every kW installed per day on average (therefore 40kWh a day with a 10kW system). If you use 10kWh of that, you will export 30kWh to the grid. The question is, how much will you get paid for that. You might be able to get 15c/kWh if you’re lucky, that’s $4.50 a day, $1650 a year. You should be able to fill in the assumptions where needed there, and hopefully work out if it is a worthwhile investment or not. If would come down to the extra cost of the bigger system, and how much you’ll get for the feed-in tariff (FIT).
Just to come back to your original comment here. It looks like those calcs assume that you will consume all of the solar that you produce. As you mention, that’s unlikely because you don’t use that much. It’s better to blend what you pay for energy (assuming that’s $0.28/kWh), and what you will receive when you export ($0.??). Let’s say you consume half of your solar energy, and export the rest, you’ll want to blend your cost of solar with your FIT 50/50, so if the FIT is $0.14, then your blended value of the solar will be $0.21 = ($0.28 + $0.14 / 2). Does that make sense?
I’m not really following this quote to be honest. I don’t see any batteries. Looks pretty dear.
It’s very tough to weigh up I find. I really like the Enphase micro inverters, you will get more solar out of them. Given any extra solar you produce will only give you whatever your FIT rate is though, it may be less compelling. It would be more compelling if you were able to offset your more expensive cost of buying energy. Read this thread for more Micro inverters (Enphase ) Vs Power optimisers (SolarEdge, Tigo) - #4 by Marty.
Last thing you might want to read if you are getting a bit confused about kW & kWh: ⚡ Solar Power vs Solar Energy - kW & kWh explained.
Hope that helps!
Marty