Sizing your solar system for South Australia

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For first time solar buyers, you may wonder how to size your solar pv system. This is important as you might not install enough solar panels to justify the energy savings, this also applies the other way as you might install too many solar panels.

The amount of solar you would want, depends on:

  • Your energy usage
  • Your estimated savings and payback period
  • How much sunshine you receive in your location?
  • Angle and orientation of your roof, any potential shading
  • How much energy you consume in the winter/summer seasons

There are certain restrictions on the sizing of solar panels in Australia, you are unable to exceed 30% more than your inverter capacity and there are also limits on size of inverters depending on your house being single or triple phase. We will explain more below.

Determine your energy consumption


Take a quick look at your energy bill and you can see how much energy is being used daily. Your energy meter, however, records your energy usage every quarter (3 months) and calculates the average usage daily. When sizing your solar PV system, you would want to install enough panels to generate enough cover your bills as much as you can.

There are about 4.2 sunlight hours per day on average, so for every 1 kW of solar panels it would output 4.2 kW daily. Even though there are 9-10 hours of sunlight, your panels output will fluctuate so 4.2 is the average amount of energy the panels will use. So, to figure out the amount to size your system, divide your average daily usage by sunlight hours.

For example, say you use 20 kWh daily, divide that by 4.2 sunlight hours and divide again by 2, assuming you use 50% of that 20 kW during the day, a 2.5 kW system would be suitable.

Solar Panels only generate energy during the day

Keep in mind that solar panels can only generate energy throughout the day, excess energy generated not used by your household during that time could be sold back to the grid as a feed-in tariff. Obviously, you don’t use all your electricity during the day, your situation might be that you are away during the day and use most of your power during the night. Your energy requirements might differ so it is best to consult a solar company to tailor a system suited to your needs. Unfortunately, your power bill does not record your energy usage on an hourly basis so you would have to do this step manually. Read here to find out more.

Energy storage systems are able to save up excess energy you use during the day, so that you can use them at night. This may change the recommended size of your solar system; however, battery systems are quite expensive and unless you have the cash, are ill-advised as of now.

Energy saving tips

Here are a few tips to reducing the amount of energy you use, maximizing your energy usage during the day.

  • Consider using the timer function on appliances such as the washing machine, the dryer and the dishwasher and set them to operate during the day.
  • Consider buying power point timers to limit the amount of energy you use during the night.
  • Have a timer on light switches to make sure they are off whenever they are not in use. Also consider changing all your light bulbs to LEDs as they are more energy efficient.
  • Don’t leave your mobile phone plugged in overnight, it only takes a couple hours to charge, consider charging it at your workplace or during the day as you are getting ready to start.

Physical space

You may have a lot of space on your roof, or you might be limited. The size and type of solar system will depend on the amount of space you have available. For example, in order to install a solar system with an average output (5kW), you will need 20 panels which would require an area of 30m² to produce enough energy for most homes If you’re putting panels on your roof, direction can be a consideration. East or west-facing roofs would be naturally more sunny than north-facing ones, which will affect how many panels you’ll need

Solar Panel restrictions

Most electrical distributors allow up to 5 kW for single phase and 30Kw for three phase (commercial premises). This limit applies for inverters, so you could install larger panel arrays but you are limited by your inverter.

if you can afford it, you would want the most amount of solar you can fit on your roof (or allowed by your electricity distributor), this is about 6.6 kW of panels with a 5 Kw inverter. This is the largest system you can have with a single-phase household. This would cover most people’s electricity needs; the upfront cost is reasonable and the payback period is very good.

An inverter converts DC electricity to AC electricity that is usable by your household appliances, due to the inverter limit there is only so much an inverter is able to convert so they are your limiting factor.

You have a limit of up to 5 kW inverter on most residential households, so to maximize your energy output based on that restriction, it is advised to oversize the number of panels to get closer to that 5 kW output.

People generally don’t go over 6.6 kW with a 5 kW system because government rebates have a restriction of STCs given to panels only up to 30% more than inverter capacity. So having more additional solar panels would not net you additional STCs and would be a waste. Read up more on STCs here.

Read here to learn how to calculate payback periods, you would want to size your system accordingly to your budget and the best payback period to justify your investment.

Natural Technology Systems are solar providers that have been in business for over 30 years, we are a business that South Australia trusts and provide expert, obligation free quotes and advice. We provide customers with the most cost-effective way to slash those power bills for your home or business.

Click here for a quick quote for your solar power needs or contact us today at (08) 7081 9830 You can also email us for expert, obligation-free advice

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