How to Size a Solar PV System:
Investing in a Solar PV System can be a wise decision for every residential or commercial property owner in Australia. The latest technology Solar PV Panels and Solar Inverters are easy to install and operate, cheap to maintain, and offer long-term performance and energy savings.
The size of a rooftop Solar PV System refers to the total power-generating capacity of all the solar panels, measured in watt-hours (Wh) or kilowatts (kW); One kilowatt (1 kW) = 1000 Watts. It depends on the number of solar panels and the rated capacity of the panels. For instance, a Solar PV System might include 15 x 440 Watts panels so the system size would be 6,650 Watts or 6.65 kW.
To make the most out of your Solar PV System, you need to correctly size the system by considering the following:
- Your Energy Usage
- Electricity Pricing
- Number of Hours of Sunshine in Your Area
- Roof Orientation
- Roof Space
- Electricity Generated by Solar PV Panels
- Your Budget
- Network Limitations
- Bigger is Always Better
Your Energy Usage:
A typical Australian home uses 11 kWh to 23 kWh daily on average. However, it can vary depending on the number of occupants at a particular property, the area of the property, usage of gas and/or electricity for cooking and/or hot water, various types of electrical appliances, pool or spa, season – winter or summer, and so on.
One should also consider the timing of the electricity usage, such as working-class people during the weekdays, mostly remaining at work, however, weekends are the main power-hungry days for them as everyone is at home and uses most of the power during the daytime. Also, they run high-power-consuming appliances during weekends, like washing machines, dryers, vacuum cleaners, etc. In contrast, for retired people, the usage can be similar for all days. In the case of acreage houses, water pumps, and septic tank pumps are the main power killers, they run throughout the day. Further, people use more power in summer to run air conditioners (especially in warm areas) and heaters in winter (especially in colder places).
You should also think about your future plans:
Source: http://www.bom.gov.au/watl/sunshine/
It is evident from the image that a system installed in Alice Springs can provide the highest production, followed by Darwin and Perth, then major metros like Brisbane, Sydney, and Melbourne respectively. Whereas, one installed in Hobart can give the lowest output.
Roof Orientation:
Again, the roof orientation has a direct impact on the daily, weekly, monthly, or annual output of a Solar PV System. Solar PV Panels can be installed on rooftops that face north, east, or west, which are ideal directions. However, in some cases, they can be installed facing south too, if there’s no room to install them facing any other direction.
North-facing rooftops receive sunlight throughout the day and generate the maximum electricity; followed by the north-west, north-east, or east-west orientation. Panels facing east will generate maximum power in the morning while those facing west generate maximum later in the afternoon. Panels on south-facing roofs can generate less electricity, especially in winter months. But something is better than nothing. In such cases, one can think about installing Solar PV Panels on tilt frames to face them north.
Source: https://www.energy.gov.au/solar/get-know-solar-technology/solar-panels#size-of-solar-panels-3
A rough estimate of energy produced (in kWh) by different size Solar PV Systems / Solar PV Panels in each state of Australia:
| System Size | VIC | NSW | QLD | SA | WA | TAS | ACT | NT |
| 6.6kW | 23.8 | 25.7 | 27.7 | 27.7 | 29.0 | 23.1 | 28.1 | 29.0 |
| 10kW | 36.0 | 39.0 | 42.0 | 42.0 | 44.0 | 35.0 | 42.6 | 44.0 |
| 13kW | 46.8 | 50.7 | 54.6 | 54.6 | 57.2 | 45.5 | 55.4 | 57.2 |
So, a bigger system is always better to make it future-proof.
Your Budget:
Your budget is one of the important factors in deciding the size of a Solar PV System or brand or quality of Solar PV Panels and/or Solar Inverters.
The Federal Government’s small-generation unit rebate scheme offers small-scale technology certificates (STCs) point-of-sale rebates on the size of Solar PV Panels. Hence, a bigger size of Solar PV System can grab a higher rebate due to the larger size of Solar PV Panels. REC Registry STC Calculator
- Going to start working from home more often
- Family planning
- Addition of Swimming Pool, Spa, or Ducted Aircon System
- Switching from Gas to Electricity for cooking and/or hot water
- Buying an EV
- Build an extension at your place, a shed, a granny flat, etc.
Electricity Pricing:
The more you pay for power bills, the more you can save with the Solar PV System. Your electricity plan reflects a big difference in your savings after the installation of a Solar PV System.
So, if the electricity prices are higher or expected to skyrocket, a bigger Solar PV System may be cost-effective because it can generate more power. In a way, it can reduce your need to buy power from the grid. In addition, you might export more power to the grid from it, hence, your electricity retailer pays you a high feed-in tariff. Owing to this fact, nowadays many people opt for a 10 kWh Solar PV System instead of a 6.6 kWh one.
Number of Hours of Sunshine in Your Area:
The number of hours of sunshine in your area has a direct impact on the daily, weekly, monthly, or annual output of your Solar PV System. In other words, a greater hour of sunshine means more output.
Please refer to the following image to check the average daily sunshine annually across Australia:
If a rooftop is shaded by tall trees, surrounding buildings, or other obstructions, a system installed on it can generate less electricity. A little shading is not necessarily a problem, but a long period of shading can significantly reduce the system output.
Last but not least, panels on pitched roofs can generate more power than the ones installed on flat or lightly sloping rooftops.
Roof Space:
Knowing the available roof space on a particular property is important in determining how many panels we can install. If you have more roof space, it is always better to install a larger system to make it future-proof. But if the roof space is an issue, you should consider a smaller Solar PV System or a system with higher-rated panels (provided suitable for the roof type).
Typically, the dimensions of residential Solar PV Panels are around 1.1 meters wide by 1.7 meters long. Some solar panel brands offer bigger panels, but they may not be suitable for all roof types. Commercial Solar PV Panels come in dimensions of around 1.1 meters wide by 2 meters long.
Hence, a typical 6.6kW Solar PV System including 15 X 440 Watts Solar PV Panels requires roughly 30m2 roof space. A 10.5kW Solar PV System with 24 X 440 Watts Solar PV Panels will need roughly 47-48m2 roof space, and a 13.2kW Solar PV System with 30 X 440 Watts Solar PV Panels will need roughly 60m2 space.
Electricity Generated by Solar PV Panels:
The electricity (or electrical energy) generated by solar panels is measured in watt-hours (Wh) or kilowatt-hours (kWh). In Australia, on average 1kW of Solar PV Panels can generate between 3 kWh and 5 kWh per day, depending on the location, number of sunshine hours, the slope of a rooftop, the facing of the panels, etc.
The following table reflects a typical amount of electricity generated by 1 kW of Solar PV Panels per day in different Australian locations, averaged over a year. Solar PV Panels may produce more than that amount in summer and less in winter.
It is said, “If you buy cheap, you buy twice.” In turn, if your budget allows you can buy better quality Solar PV Panels and Solar Inverters, like Fronius – European Solar Inverter or REC Solar Modules – one of the top-end solar PV Panels.
Network Limitations:
In most areas, the local distribution network service provider puts a cap on the size of the rooftop solar system inverter which can be connected to the grid and/or the amount of electricity that can be exported to the grid from rooftop solar.
A connection limit restricts the size of the inverter that can be connected to the grid. Generally, it depends on the phase of your electricity connection – single-phase, two-phase, or three-phase supply. For example, if the connection limit is 10kW per phase, you could connect a 10kW inverter if your property is connected to a single-phase powerline. If your property is connected to a three-phase connection, you could install a three-phase inverter up to 30kW or a 10kW single-phase inverter to each phase.
An export limit restricts how much excess electricity you can feed to the grid from your Solar PV System. This may be applied to each phase and lower than the connection limit. If your inverter is bigger than the export limit, you might need to set up an export limitation for the inverter. For example, the distribution network service provider may allow a 10kW single-phase inverter max per phase, but with the export limited to 5kW.
Bigger is Always Better:
If you have the roof space and budget no issue, we always insist on going with a larger system size.
A larger Solar PV System with a bigger Solar Inverter:
- might get the Return on Investment (ROI) faster on a bigger system due to higher output
- might get high feed-in credits due to higher export
- might turn cheaper in terms of value per kW compared to a smaller one
- might be a good option if you plan to install a battery pack at a later stage
- might be a good option for future-proofing, if you have a plan to buy an Electric Vehicle (EV).
To avoid all these hassles, simply contact SOLPOWER AUSTRALIA at 1800 979 707 or click on Get Quote, and one of our friendly team members will help you by designing a system perfectly suitable to your needs.
