A Solar Expert Provides Advice on Residential Off-Grid Solar Systems

A Solar Expert Provides Advice on Residential Off-Grid Solar Systems

I have happily lived off-grid for the last four or so years. However, our household’s solar system has been increasingly pushed to its limits as I am now working entirely from home and both my future in-laws are living permanently in the second residence on the property. Energy consumption has therefore increased given the extra number of humans the system needs to support. More electronic items such as laptops and smartphones are being used, as well as other energy-sucking devices such as a desktop computer. The added pressure on our solar system means we’ve had to run the diesel generator every other day; annoying since the point of living off-grid independent of electricity companies is to reduce our reliance on fossil fuels.

Since the current system isn’t supporting us very well, and my in-laws require a fridge in their residence, we’ve made the decision to increase the capacity of our existing home solar system, which means getting more solar panels as well as more solar batteries in which to store the energy.

Now when Finn Peacock, the founder of one of Australia’s top solar power websites, SolarQuotes, released his new book The Good Solar Guide: 7 Steps to Tiny Bills for Australian Homeowners I thought it presented a good opportunity to ask this solar expert a few home solar-specific questions, particularly since we’re in the middle of improving our off-grid solar system’s capacity.

EWP: What type of battery do you think is best for a residential off-grid setup?

Finn Peacock: Here in Australia, it looks like the optimum payback for a typical energy user is a 6-7kWh battery – ideally with 5kW of power. Something like the LG Chem RESU 6.5.

If you are not focussed on optimising payback but simply want to minimise your reliance on grid electricity then a bigger battery like [Tesla’s] Powerwall or a Sonnen with around 13kWh of storage can get a home up to 95% self-sufficient.

Related Post: 5 Reasons Why I Love Living Off-the-Grid

An Expert Provides Advice on Residential Off-Grid Solar Systems
Additional solar panels to add to our existing system to increase its capacity.
An Expert Provides Advice on Residential Home Off-Grid Solar Systems

EWP: What size and type of cable to use from solar panels to the inverter?

FP: You use special DC Cabling to go from the rooftop DC Isolator to the inverter. The length of this cabling will vary with every job, and a CEC accredited designer will do the calculations to ensure it is a suitable size. Typical sizes are 2.5, 4 6 and 10mm2.

Related Post: Are Solar Panels A Middle-Class Purchase? This Survey Says Yes

EWP: We’re big on reusing and purchasing secondhand and have been advised that we can’t mix and match panels. Why can’t we use one set of panels and mix with another set?

FP: In theory, you can – if they are electrically similar. In practice – if you want to connect your solar to the grid you generally can’t use second-hand panels if they are more than a couple of years old as the particular model numbers are probably not on the ‘approved product list’ any more. Save them for camping or off-grid systems.

EWP: Since the Paris Agreement, Australia is committed to sustainability policies and we see more solar farms being built across the country. Do you think people should invest in solar panels or just wait for a solar farm to be built that feeds renewable energy back into the grid?

FP: If you don’t want to install solar – but want to have a carbon-neutral energy supply – then the best option is to buy ‘Green Power’ through your regular grid connection. This guarantees all the electricity used has been sourced from renewables and raises funds to build more solar and wind farms. Environmentally it is as effective as buying your own solar panels. So go for it! It’s not as much fun though.

Tesla's Powerwall 2 Home with Solar Panels
Powerwall 2. Credit: Tesla

EWP: What is the average cost range of a brand new solar setup these days?

FP: A typical solar system is 6.6kW with a 5kW inverter. This costs around $5,000 to $9,000 depending mostly on the quality of the hardware used.

Thanks for all of your help Finn! This information will come in very handy when we further develop our existing off-grid solar system and make it fit the needs of two households.

Keen to learn more about installing home solar? You can purchase your copy of The Good Solar Guide, click here. You can also access basic information on home solar systems at solarquotes.com.au.

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