June 13th, 2019

Owner Builders and Solar Power

Over the last few months, several of my owner builder students have been asking what I know about solar.

Fact is, I actually do know a little, having recently installed a 6.5 kilowatt system at my own home.

6.5 kilowatts is 24 panels and the single inverter which sits nicely on my West North West facing roof.

Owner builders need to consider several things if they are looking to install solar.

Firstly, as an owner builder, you are not legally allowed to do any of the works associated with the installation of your solar system, unless of course you are a licensed electrician with solar accreditation. That should be obvious.

The second thing is deciding what size system will best suit your needs. Thee is some confusion out there generally as to how big a system you can install, with many owner builders thinking that 6.5 kilowatts is the maximum for a single residential property. Fact is you can go bigger but they need to be separate systems.

My son has two systems, that means two inverters and around 48 panel to generate the level of power that he wanted to achieve. He is a licensed electrician and does run a solar installation company, so he did have a slight advantage.

Other factors that should be considered are how and when you use your electricity, what your exposure to sunlight is and what type of roof you have.
How an owner builder will use their electricity is important, particularly because the rebates given these days is far lees than in previous years, so your aim should be to use as much of the electricity that you produce. Retail prices of between 25 to 40 cents per kWh are typical and sales back to the grid will yield you around 16 cents.

If your place is electrically ‘noisy’ through the day, then it makes sense to generate and use as much as you can during daylight hours. We advise our owner builders to run pool pumps, washing machines and dishwasher during peak production times to get the best out of their systems.

The ideal orientation is close to North for these latitudes and the angle of installation can be optimised by matching the latitude so for someone in Cairns they would set the panel pitch at around 17 degrees, 27 degrees for Brisbane and 38 degrees for Melbourne. Owner Builders should check that this is correct, because it may be old thinking and the technology has come so far that it may not still be relevant. That’s the way it was taught to me anyway! (Fraser?).
In any case there are other factors like shade from trees and obstructions that will affect exposure and hence production.

Owner Builders need to be aware that not all panels are equal and that a cheap system may be a nasty system and not provide the same output as a good quality set up.

Of course, the question most often asked is how much will I save?

Well it depends on all the factors I have mentioned above but as a guide, and by my owner experience, the 6.5 kWh system that I have installed has reduced my power bills by around 70%. This is inclusive of a 28% discount I got by changing suppliers at the same time.

So, owner builders need to shop around and get the best deal not only from the installation companies but also through revisiting their retail supplier.

Hope this demystifies solar installation to some extent.
As always,

Best Regards and Happy Owner Building

Rick