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Owner Builder Blog

June 13th, 2019

13/6/2019

6 Comments

 
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
6 Comments
Brenton Pugh
30/1/2020 03:31:18

Great read

Reply
Bradley Tronc
13/2/2020 13:09:19

I love my solar.

We have no mains power at our little property. The closest transformer was 200 - 300 metres away.

It cost us less to install a 6.5 Kw system with batteries than to get the power lines extended and a new transformer.

It was a no brainer.

The only thing I would offer as advice is not to muck around with cheaper batteries.

Get the best you can afford!

Reply
Colin Hill
19/5/2020 08:47:12

My advice is to do the maths. When I installed solar I calculated that the payback time for the panels was 4 - 5 years but a battery was 10. From this, I decided to install the panels and hold off on the battery until price allows for a faster payback.

Reply
Steve Cottrell
5/6/2020 14:04:57

Unfortunately most people don't understand the value of proper orientation of their solar panels. when we were getting 60 cents per kWh (gross metering) an orientation of direct north was great, but now with net metering, a combination of east, north and west is more efficient. Most appliances (washing machine, dryer,A/C unit will draw from 1 to 3 kWh. A 6.5kw system will provide 1 to 3 kw constantly from sunrise to sunset. Running these devices over the course of the day means that the P.V. system will adequately supply them resulting in no cosumption of power from your supplier. Think about your roof design when building.

Reply
Mark Ferian
14/9/2020 16:53:58

We have just had a 6Kw solar system installed today. The roof faces north. it is replacing a old 2Kw system. I look forward to the savings this coming summer!!

Reply
John Nash
10/11/2020 08:56:49

We had off grid solar on the house we lost to the 2019 fires and plan to be off grid again. Technology has moved on from "state of the art" 2000 systems (980w of panel and 1500w inverter output with lead acid 24v batteries) which lasted 19y to 20kw Li batteries and min 5kw inverter output. There have been some hard lessons learnt on the robustness of some components in our environment. We had a series of errors on the inbuilt battery management system which we could not access to resolve because we needed an active internet connection. It has taken the solar installer several months to configure the charge controller and batteries to prevent the battery from shutting down to protect itself. We also changed the battery to a slightly older technology that can handle the extremes of our temperature range (-7 C to +36 C) without need to provide a temp controlled environment.
In the design stage for our house we had to factor in panel number and location, battery storage and inverter charge controller location and protection plus where to place backup generator. We also had the system designed to make it easy to expand if our demand increased significantly.
The end result is one where we hopefully will not need to run the generator except for its regular test runs.

Reply



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    Author

    Rick Heaton is a Building and Construction Industry professional with formal tertiary qualifications in management and training.

    With over 30 years assisting Owner Builders, he brings an easy style to providing information and advice to our students.

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