We previously wrote an article about the feasibility of an Australian home going off-grid with a 3kW solar system – quite a small system size for such an ambitious endeavour. In this article, we’ll look at the case for developing off grid power systems with a 10kW solar system – the unofficial upper limit for residential solar system size in Australia. Can an Australian home disconnect from the grid with a 10kW solar system and batteries?
(This article was originally published in March 2016. We have updated it for clarity and simplicity.)
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Is energy self-sufficiency possible with a 10kW solar system and batteries?
We’ll assume that you live in a home with a 10kW solar system and no solar feed-in tariff incentive, meaning that you are better off ‘self-consuming‘ your solar energy than sending it into the grid. Whether or a not a home could sever ties with the grid with a system of this size depends on a number of things, including:
- Location: Some locations are just sunnier than others. Darwin is the sunniest of all of Australia’s capital cities, while Hobart is the least sunny.
- Roof orientation and tilt: In Australia, north-facing rooftops whose tilt is roughly at the same angle as the location’s latitude produce the most power. East and west-facing arrays tend to produce a bit less, and south-facing arrays least of all. (Read more.)
- Daily energy consumption: If your daily energy needs are minimal (e.g. under 10 kilowatt-hours – kWh – per day), it will be easier for you to install a solar+storage system that can make you self-sufficient.
- Daytime energy consumption: If you use most of your electricity while the sun shines, you won’t need as large a battery bank because you’ll likely consume the solar energy directly, as it is being produced. (Read more.)
- Total solar energy produced: Remember that if you want to go off-grid, you’ll need to be able to store enough energy to get you through 3-4 days of rainy weather – this is called ‘energy autonomy’. If your solar PV system is not large enough to charge your battery bank, then you can’t go off grid without a generator, which could increase the overall cost of your system significantly (mainly because of the fuel expenditures).
Please note that the figures below are estimates only and should not be taken as final-word advice. Please speak with a solar/storage installer before choosing your final system size and products.
Going off-grid with 10kW of solar and batteries (Sydney example)
Using SunWiz’s PVSell software, we took a look at the case for going off-grid with a 10kW solar system in Sydney below. The primary thing that we’re looking at is the ‘one day storm blackout protection’, which is a good indication of how much energy independence – and therefore off-grid readiness – that a solar & storage system can deliver. It’s also useful to look at the ‘energy self-generation’ figure, which shows the percentage of energy the 10kW solar system would produce relative to the amount of energy the home consumes.
Example: Going off-grid in Sydney
- Unshaded, north-facing 10kW solar system
- 10kWh daily electricity consumption (assumes heating & cooling are done using non-electric means)
- Mostly daytime usage
Daily energy balance (10kW storage and 50kWh storage):
The verdict: Off-grid with 10kW of solar? Definitely possible
As you can see, it is clearly feasible for households with low electricity consumption (10kWh per day) to cut ties with the grid with a 10kW solar system and some batteries. In fact, 10kW of solar may actually be overkill in many of these cases when energy consumption is only 10kWh per day – meaning there’s plenty of room for the home to use more energy, either on occasion (e.g. during parties) or regularly (e.g. as the number of people living in the household grows). Even if their average daily electricity consumption rose to 15kWh per day, the solar PV system would still produce enough energy to meet the home’s energy demand.
Of course, one thing we haven’t talked about here is cost. Although a 10kW solar system will typically cost between $10,000 and $15,000, the batteries will be a bit more expensive (indicative prices here). Additionally, there are a number of other things that homeowners thinking about going off grid should take into consideration.
One positive is that you don’t have to go off grid to benefit from solar & batteries. Actually, having a grid-connected solar & storage system might be a better investment, while still affording the owner a large degree of energy independence (and giving you the reliability of having the grid as a ‘backup’ source of energy).
- Solar & battery storage system sizing: A quick guide. (Includes a useful, indicative solar & battery storage system sizing table.)
- Play with the numbers yourself with our Battery Storage Sizing & Payback Estimator tool or our Off-grid Solar & Storage System Sizing Estimator
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