One of the first decisions a household considering solar will need to make is the capacity (in kilowatts, kW) of the system to be installed. Two of the most popular residential solar PV system sizes in Australia are 3kW and 5kW. Which system size is the better investment – and why?

You’ll save the most by using your solar directly

These days, getting the most out of a solar PV system means using the energy directly in your home – ‘solar self-consumption‘. By putting the solar energy go good use within your home, you avoid the need to purchase electricity from the grid – at a rate between 18-35c per kilowatt-hour (kWh), depending on where you are (as per the table below). By contrast, exporting solar energy into the grid will earn you only about 6-8c/kWh. Read the full article →

{ 4 comments }

Lukasz 3 May, 2017 at 7:18 am

I think you need to revist your Electricity consumption charge ($/kWh incl GST) in Victoria. No where near 18 cents inclusive of GST. And what about the service supply charge, and feed in tarrif. Why are those two not incorporated into the payback time.

Solar Choice Staff 15 May, 2017 at 10:32 am

Hi Lukasz,

We’ll look into the issue with the consumption charge (which does indeed seem to be low). As for the feed-in tariff rates, they are incorporated into payback times (and keep in mind that this article was written before the Vic gov’s announcement that they’ll be raising feed-in rates). As for supply charge, we only include this in our calculations where we are comparing different energy plans (e.g. one retailer might have a higher rate than another) or when comparing being on-grid vs off-grid.

Keep an eye out – will be updating this article soon.

will 1 March, 2017 at 9:48 pm

hi there.
why has there not been any sun solar roof top tracking available? i know they are only available for ground mounted solar systems.
you can gain 10-30% plus efficiency? i know it will be cursed by the wind, why cant you make one when there is high wind it goes flat and when its low or no wind it goes back to the tracking angle to the correct optimum efficiency facing angel to the sun. it would be much more cost effective and gain more power and pay it self off quicker also in the long run. i think it wont cost much more.
also if its expensive to be made?
i can make it my self iv got the skills in using powertools and im good in fabricating things from scratch. i just need details on how to make it and then supply it to the solar installer.

our average cost on our house is $4 day with no ducted aircon off and then it goes upto $8 day when on, so want a system where it will cover all day time running and then add battery storage latter on for night use. is 7kw big enough or bigger is needed? also i think we got 3phase also because of the big AC unit i think its 10kw plus from meomory.
(also got normal appliances such as microwave/electric oven/2 fridges/multiple tvs/multiple PC/got seiling fans/led lights in the whole house/ etc) its a massive double story house

i live in western sydney by the way

and also i heard it better to overclock your inverter then to have less power going in to it, is that right?

i also want to know how long will it take for it to pay off please give me your calculation of the average system cost and pay off with solar tracking and with out and with battery combination in both setups with solar tracking and with out. thanks sorry to ask to much but i want to know and i guess also other people want to know also

Solar Choice Staff 6 March, 2017 at 10:35 am

Hi Will,

Lots of points to address here so I’ll break them down in chunks below.

-Rooftop solar tracking doesn’t really make a ton of sense these days given how affordable solar panels have become. Instead of adding tracking (which introduces moving parts and the possibility of breakage), it’s usually easier and more cost-effective to simply tack on another panel or two to increase overall system output. If you’re keen and confident that you can make a tracking system yourself, don’t let us stop you though!

-If you want to know more about battery & solar system sizing, check out our Solar PV & Battery Storage System Sizing & Payback Estimator tool. That will help you get an indicative idea of what size system you might need – although you’ll ultimately want to consult with some solar pros to get into the details (you can get quotes from installers here). Off the top of my head, I’d say that 7kW is probably plenty, but you might need larger if your AC unit is indeed 10kW (which is massive!)

-You can read about inverter overclocking here and here. Yes, it’s an officially recognised and widely used practice – and is probably a more cost-effective and trouble-free option than rooftop tracking.

-Again, you can use the PV & Battery System Sizing & Payback Estimator (linked above) to work out rough payback times. If the solar & battery system are appropriately sized (and you don’t pay too much for it), then you should be able to get a payback period well under 10 years. We recommend going with a small battery system to start out with, as smaller systems are more likely to have a shorter payback period.

Hope all this helps, and good luck with your project!

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