(Nectr formally known as InstyleSolar)
What Solar Panels Do I Get? How Many Do I Need?
There are multiple brands of solar panels in the Australian market, and having so many options can cause confusion at first. However, there is a quick way to identify the best solar panels: looking for products that are approved by the Clean Energy Council (CEC).
You might also be wondering what is the ideal number of solar panels for your home, and the answer depends on several factors:
- What is your quarterly power bill? How many kilowatt-hours of electricity does your home consume each year? As the energy needs of a property increase, the number of solar panels required to cover them also increases.
- Do you want a power source that is also available at night and during blackouts? If you want to use solar electricity at night, you need a battery system to store it during the day. This also means you need additional solar panels to charge the battery.
- What is the specific brand and model of your solar panels? Not all solar panels have the same wattage, and this depends on the model and brand. If you choose a solar panel model with high wattage, you will need less of them to reach a given capacity. For example, you can reach 6.6 kilowatts by installing 20 panels with a capacity of 330W each, or with 22 panels rated at 300W.
When a home solar system is optimally sized, according to your electricity needs, it offers a better financial return. If you have too few solar panels, their kilowatt-hour output will be small compared with your consumption, which means your power bill savings will also be small. On the other hand, an oversized solar system produces a lot of electricity that you don’t use, which gets exported to the local grid. Electricity providers give you credit for this energy, but the feed-in tariff they pay is much smaller than the retail tariff they charge.
Nectr can design a solar power system of the optimal size for your home, based on a professional assessment of your roof and electricity bills. We can identify the areas of your roof that get the most sunshine throughout the year while avoiding shaded areas where solar panels are less productive. Using this information, we can calculate the ideal number of solar panels for your roof, and design an optimal layout. We only work with CEC-approved solar panel brands like Q CELLS, Canadian Solar, Jinko Solar and Risen.
What is the ideal size of a home solar system?
A home solar system can only be designed properly after a professional assessment. However, you can estimate the number of solar panels required, based on your electricity bills and local sunshine. Here we will provide a simple procedure you can follow, but keep in mind this is only a quick calculation and not a replacement for a professional solar design.
The first step is knowing your annual electricity consumption, and you can find this out by adding your four most recent quarterly bills. Remember you need to add the kilowatt-hour amounts, not the dollar amounts paid, since the output of a solar system is measured in kWh. Each home has a unique energy consumption profile, but the following are some factors that increase consumption:
- Having a large home
- Having a household with several members
- Having a pool, since the pump consumes electricity every day
- Having old and inefficient appliances
- Working from home
Your home solar system can be sized based on your annual kilowatt-hour consumption. For example, if your home uses 15,000 kWh per year and you want to go 100% solar, you need a system that will generate this amount under local sunshine conditions.
How much sunshine is available in your location?
The Global Solar Atlas from the World Bank is a very useful tool when you need to estimate the productivity of a solar panel system. You can search for your home’s location on the map, and you can click to display several metrics about solar radiation. The exact metric you’re looking for is the specific photovoltaic power output, which is first on the list when you click anywhere on the map.
For example, if the Global Solar Atlas shows 1,600 kWh/kWp for a specific location, it means each kilowatt of solar capacity (kWp) will produce 1,600 kilowatt-hours per year. In the case of a 6.6-kW system, you can estimate the annual output by multiplying both values.
- Annual electricity production = 6.6kW x 1,600 kWh/kWp = 10,560 kWh
- The unit kWp means “kilowatts peak”, and it describes the rated capacity of a solar power system.
- The letter “p” is used to indicate peak capacity, since the actual wattage changes throughout the day, depending on how much sunlight is received by each panel.
If you zoom into Brisbane QLD using the Global Solar Atlas, you will find that the specific photovoltaic power output ranges from 1,500 to 1,700 kWh/kWp (depending on the exact location where you click). This means a 6.6-kW home solar system can be expected to generate between 10,000 and 11,000 kWh per year in Brisbane.
Estimating the size of a home solar system
You can also perform the opposite calculation: when you know how many kilowatt-hours are needed, you can divide that value by the specific PV power output. In this case, you get the estimated size of your home solar system.
- Assume your home uses 12,800 kWh per year, and your location has a specific PV power output of 1,600 kWh/kWh according to the Global Solar Atlas.
- Dividing both values, we get an estimated solar system size of 8 kilowatts.
As mentioned above, this is a very simplified calculation. We aren’t considering factors like your roof material, its pitch and orientation, and shading issues. However, all these factors are taken into account when you get a professional design and installation from Nectr.
At this point, we have estimated the kilowatts of solar capacity needed by the home in our example. However, how many solar panels are needed to reach this capacity? The answer will depend on the rated wattage of the solar panel model used for the system.
The following table estimates how many solar panels are needed to reach 8 kW, considering different wattages. We will also estimate the roof space needed, considering an area of 1.70 m2 per panel, which is typical for residential modules.
|Solar panel wattage
|How many are needed to reach 8 kW?
|Area covered (m2)
Note how the solar array becomes progressively larger as the solar panel wattage decreases. All the solar PV systems in this example have a capacity slightly above 8 kW, but the array with 270W panels is around 30% larger, requiring 7 additional panels.
Having a larger array is not necessarily a bad thing, especially if you have a very large roof. However, you can use space more efficiently by using solar panels with a higher wattage and efficiency. A smaller array can also be concentrated on the sunniest part of your roof, making it more productive over time.
What is the ideal layout for rooftop solar panels?
Since the sun’s position in the sky is always changing, different sections of your roof will get different amounts of solar radiation. However, there are some general guidelines that solar professionals follow when designing the layout of photovoltaic systems:
- Avoiding shaded areas of your roof whenever possible, since they have a major negative impact on solar panel productivity.
- Identifying which roof areas get the most sunshine, and using them for solar panels.
Shadows must be avoided whenever possible, for the simple reason that they block sunlight. Solar panels are much less productive when shaded, and even partial shading has a severe impact. Since all PV cells on a solar panel are in the same circuit, the shaded cells affect those that get normal sunlight. The same applies for groups of solar panels that are wired in the same string circuit: one shaded panel affects all the rest, even when they are getting full sunlight.
The effects of shading can be minimised by using a microinverter or a power optimiser on each solar panel. However, this makes your system more expensive because you need an extra device for each module. In most cases, it’s possible to simply design a solar panel layout that uses unshaded roof areas, and no additional devices are necessary.
The orientation of roof sections also has an impact on the productivity of solar panels. Australia is a southern hemisphere country, which means that the sun is on the northern portion of the sky most of the time. As a result, your solar panels will achieve higher productivity if they are set up on north-facing roof sections. Of course, this doesn’t apply when the north-facing sections of your roof are shaded, and you will achieve much better results on other roof areas.
As you might guess, south-facing roofs get the least sunshine in Australia, especially if they have a high pitch. East-facing roofs get more sunshine during the morning, since the sun rises in that direction, and west-facing roofs get more sunshine during the afternoon.
- When shading is not an issue, it usually makes sense to install solar panels on north-facing roof sections.
- However, some electricity plans have time-of-use tariffs, which change throughout the day. If you have a plan that charges high tariffs during the afternoon, a west-facing solar array may be a better option.
- The ideal solar panel orientation can only be determined after a professional assessment of your roof and power bills.
Of course, personal preferences are also important when setting up solar panels. Some homeowners like their appearance, while others prefer to install home solar systems that will not be visible from the street. Nectr can design a home solar system based on both technical aspects and personal preferences.
Which solar panels are recommended for homes?
In general, you will achieve great results if your solar panels and other systems components are CEC-approved, and if you contact a qualified provider for the design and installation process. There are many high-quality solar brands to choose from in Australia, but we prefer to work with the following manufacturers at Nectr:
|Solar panel brand
|Q CELLS is an innovative solar manufacturer with R&D headquarters in Germany, and they developed the Q.ANTUM monocrystalline cell technology. They have produced over 2.5 billion of their Q.ANTUM cells, equivalent to over 10 GW of capacity.
|Canadian Solar offers a wide product selection, which includes polycrystalline and monocrystalline modules. They have delivered over 59 GW of solar panel capacity worldwide.
|Jinko Solar is one of the largest solar brands globally, present in over 160 countries, with more than 80GW of solar panel capacity delivered.
|Founded in 1986, Risen is one of the oldest brands in the solar industry. However, they have continued to innovate over the years, and they currently have a manufacturing capacity of 19 GW.
Nectr works with many products from these leading manufacturers, and all of them are covered by solid long-term warranties. We can select a solar panel model that meets your needs, and we can design a layout that uses your roof area as efficiently as possible. Our solar installations also use CEC-approved inverter brands like Fronius, Huawei FusionSolar, Sungrow, Delta and GoodWe.
Interested in solar? By clicking below you can use our smart solar calculator to find out just how much you could save with solar, what rebate you are eligible for, and the impact you will have on the environment.
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