What system size shall I get?

So I want to talk about the question of what size system you should get for your house. So the way I see it is this, there’s basically three factors. One of the factors is your usage, so how many kilowatt hours you’re using and how much you’re spending on electricity, and obviously that’s your quarterly bill, you can see both of those things. From there we could work out what size system would give you the right number of kilowatt hours for you to use. 

The second question is your roof space. So one of these things will set an upper limit. It could be that you’ve got a very, very high usage, but you’ve got a small roof space, in which case this is the one that’s going to be a constraint for you. Could be that you’ve got a massive roof space, but low usage in which case this will be the constraint, and this will kind of set the common sense upper limit. There’s a third factor. And the third factor is, who owns the grid in your area?  

So within New South Wales, there’s three companies that own the grid, there’s Ausgrid, Endeavour. My writing is really bad, and Essential Energy. These two are the Sydney-based. So they’ve got different rules around how much solar that’ll would allow based upon whether your house is single-phase or three-phase in terms of its electrical supply into the house.

If you are unlucky, you’ll get caught and you’ll not be able to put on a system bigger than, say, 5 kilowatts. But typically in an Ausgrid area, you’re allowed to put on 5 kilowatts per phase, which means if you’ve got a three-phase power supply coming into your house, you could put anything up to 15 kilowatts on. But hypothetically, this is also going to set an upper limit on what it is that you can put on. In the center of this is kind of an overall constraint, and that’s you. 

So let’s say all of these things led to a optimal system being 10 kilowatts or 12 kilowatts, you’re also a constraint in this because your appetite for what you want to invest in solar is going to allow that or not allow it. So you might look at all that and say, “Fine, I should probably get a 12-kilowatt system, but I’m going to buy a five.” So this is just based on dollars and how much you want to invest in solar. But you have these other constraints and then you’ve got you in the middle of this. 

So one of our goals is to talk about these things, look at how you’re using power, look at your roof space, do an actual layout for you to see what we could fit on, we’re going to know based on where you are, what you’re allowed to fit on, and then make some suggestions to you about the system size. So we might come up with something that is anywhere from a 5-kilowatt system, all the way up to a 20-kilowatt system. 

So we do come across people that have absolutely massive power bills. I was speaking to a guy recently who spends $3200 per quarter on power, ’cause he’s running a 25-metre pool and three or four fridge freezers and things like that, so our suggestion to him was about a 20-kilowatt system. But your situation is different, so we would love to have a chat with you.