As more Tasmanians choose to invest in solar energy, you may find yourself wondering, “How many solar panels can fit on my roof?” Determining your usable rooftop area requires addressing several key factors, including your roof’s design, condition, and local regulations. To find exactly how many panels can fit, you’ll need to measure your available roof space, which will be calculated against the average panel size. Our guide will also explain how to determine the right solar system size for you and how to maximise your roof’s energy production.
Factors To Consider in Determining Your Roof’s Capacity
When determining your rooftop capacity, examine the following factors that affect how many solar panels will fit:
Roof construction and condition
It is important to consider how suitable your roof is for solar panels. The best type of roofing is metal or asphalt shingles. Both of these materials are a strong type of tile, and because the average solar panel weighs around 18 kg, you will need a durable roof.
Furthermore, as you add panels, in addition to frames and fixings, the overall weight of your system can easily surpass 300 kg. Older or less suitable roof tiles may not adequately support solar panels, which could lead to higher installation costs due to the need for tile replacement or specialised mounting systems.
Roof design
While flat roofs don’t have a natural angle, they can be a great design for mounting solar panels because of how straightforward the installation is. Panels can be placed easily and adjusted with mounting structures for optimal sunlight.
Sloped roofs may require careful planning to maximise space, as steep pitches can cast more shadows and reduce solar panel efficiency. It is important to work directly with your local installer to determine the best panel placement for your roof design.
Roof orientation and angle
You should only consider the side of your roof that will be able to accommodate solar panels. For example, the northern side of your roof will typically get the most amount of sunlight in Tasmania. This is due to the path of the sun, which travels mostly north of Tasmania during the day. This section should be prioritised when determining your roof’s capacity, with east and west-facing panels also viable options if north-facing is unavailable.
You should also note the angle of your panels. In Tasmania, most roofs are at a slope of 22.5 degrees; however, your panels will need to be angled slightly to ensure they capture the most sunlight possible during the day, especially when the sun is at its highest point.
Shading and obstructions
Obstructions such as chimneys, skylights, vents or antennas can all reduce your available roof space. These obstructions may create shaded areas, which reduce the amount of direct sunlight hitting your panels. Trees and surrounding buildings can also disrupt your energy production with shade, particularly during periods of peak sunlight. Consider trimming or removing trees to optimise energy production.
You should also aim to position your panels in the best possible layout to avoid these obstructions. Importantly, your solar panels have exclusion zones that dictate how far they must be installed from the edge of your roof. Generally, you should allow a minimum of 20 cm between your panels and the roof’s edge. Winds are typically strongest around the edges of your roof, and a 20 cm clearance is intended to reduce any potential wind damage to your solar system.
Solar panel mounting
You will typically need to leave room around each panel to account for your mounting hardware. This is the structure that ensures your panels are secure enough to withstand various weather conditions on your rooftop. Mounting hardware will typically add an extra 5 cm to the outside of your panels.
Local regulations
Regulations and guidelines can play a significant role in determining the number of solar panels you’re allowed to install. For Tasmanians, depending on the size of your installation, there are guidelines for adding solar panels for both residential and commercial buildings.
According to the Tasmanian Government’s Regulatory Guide, for houses, there is no requirement to get building approval or council permits if you are conducting low-risk work. This applies to the majority of residential rooftop installations, at a max of 38 m². If you move beyond these limits on a single roof structure, this is called Notifiable Building Work (NFW). Although they won’t require a full building permit from the council, they must be overseen by a building surveyor. Note: If your solar panels are split across separate roof sections, they typically won’t require an NFW. However, it’s always best to check with your local council if unsure.
For commercial buildings, local regulations dictate that you are a medium-risk regardless of the size of your installation, with requirements to engage with a building surveyor to ensure you comply with government standards.
Your local installer will typically organise these steps and should be consulted if you have any concerns.
How to Calculate How Many Solar Panels Will Fit on Your Roof?
To accurately size the amount of solar panels that will fit on your roof, you’ll need to follow our 3 steps below:
Step 1: Understand the Solar panel size
Size can refer to two different things. The power output of your solar panels is measured in kilowatts (kW). It can also refer to the physical size dimensions of each panel, which is the number you’ll need to determine your usable roof space.
Everyday household panels will typically come in standard length and width measurements of 1.7 m x 1.0 m (170cm x 100cm). If you’re purchasing commercial panels designed for businesses, they may be slightly larger, at 2.1m tall x 1.1m wide (or 2.3 m²). For our calculations, we will be referring to the standard residential panel size of 1.7 m².
Step 2: Determine Your Available Roof Space
This section will require your calculations. Available roof space refers to how much area on your roof can be utilised by solar panels. As previously mentioned, obstructions such as chimneys, skylights or roof windows can all affect your area, as well as parts that are constantly shaded.
If you’re unsure about your roof space, you can work this out by multiplying the length and width of your roof to calculate its total square metres. From here, you will need to determine how much space is taken up by chimneys or shade, and deduct that from your total area.
The average roof size in Australia is typically between 120 and 200 m². For our calculations, we will use 160 m², assuming minimal roof obstructions. With one side of your roof offering much higher electricity production than the other, your optimal usable space (assuming your roof isn’t flat) is going to be approximately 80 m².
Step 3: Make the calculations
If you want to work out your usable roof area, simply use our formula below.
- Usable roof area (m²) ÷ Panel area (m²) = Estimated number of panels
Using the examples above:
- Usable roof area (m²): 80 m²
- Panel area (m²): 1.7 m²
- Estimated number of panels = 80 ÷ 1.7 = 47.1
So, based on our calculations, you have enough space to fit 47 panels on your roof. With each panel producing 0.4 kW of peak power, this gives a total capacity of 18.8 kW (47.1 x 0.4), which is more than enough to meet the energy needs of an average household.
Although every roof is different, with different challenges that may impact your usable area and reduce your number of panels. It’s always best to contact our helpful team at Tasmanian Safer Solar (TSS) here for further assistance.
How Many Solar Panels Do I Need?
Once you’ve found how many solar panels can fit on your roof, you can then determine how many you’ll need. The size of your solar system will depend on the following factors:
Energy Usage
Consider your electricity usage to discover how much energy you will need your solar panels will need to produce. The more electricity you use, the bigger the solar system you’ll need. The simplest way to find this information is to look at your past electricity bills, which will show how much power you’ve used in the previous month or quarter. Using this information, you can determine your daily energy usage in kWh (kilowatt-hour), which your solar installer will use to determine the correct amount of solar panels.
Within Tasmania, the average energy usage per day is approximately 23.61 kWh, but households can vary depending upon the number of people, location or how much they rely on heating and cooling.
Location
Your geographic location directly impacts solar panel sizing, as the availability of sunlight varies by region. Since solar panels depend on sunlight to generate electricity, areas with more sunshine will produce more energy than those that have shorter daylight or are frequently overcast. For instance, a 6.6 kW system in a sunny region such as the Gold Coast may generate 28 kWh. Whereas in Hobart, where there is generally less sunshine, it could be closer to 23 kWh.
This is important for sizing your solar system, because if you live in a cloudy region, you will have to increase your number of panels to offset the energy losses during less sunny days.
Budget
The more solar panels you install, the higher the upfront costs, so it’s important to determine how much you’re willing to pay. On average, you should expect a 6.6 kW system, which is considered a normal size for the average household, to be priced at about $11,300.
Although there are rebates and incentives to help you invest in the best system size for you. This includes the Energy Saver Loan Scheme, which provides interest-free loans of between $500 to $10,000 to cover the initial costs. There is also the federal government’s Small-Scale Technology Certificates (STCs) program. This allows eligible households to reduce the cost of solar panels by approximately 25-30%, though this is an average, and the exact amount will depend on your location and system size.
Furthermore, installing solar panels reduces your reliance on purchased electricity. This will allow you to offset the initial cost over time through savings on your energy bills.
How Can I Maximise My Roof’s Solar Potential?
To get the most out of your solar panels, consider the following tips:
Positioning your panels to maximise sunlight
It is important to ensure your solar panels are placed in a location that receives the most sunlight exposure throughout the day. Within Tasmania, installing your solar panels facing as close to north will typically provide the highest energy production. You should also consider positioning your panels away from any potential shade from nearby trees or buildings.
Getting the correct tilt angle on your panels will also be vital to boosting their production. As previously established, we recommend Tasmanians have their solar panels angled at 43° to maximise their roof’s solar potential.
Invest in energy-efficient appliances
Choosing to install more efficient solar panels, with a higher power output per square meter, will improve the total power output of your available space.
Let’s use an example: Monocrystalline panels are a type of solar panel made from single silicon crystals, characterised by their dark black colour. They differ from polycrystalline panels, which, unlike monocrystalline single silicon crystals, are composed of multiple silicon fragments and have a more traditional blue appearance. Importantly, monocrystalline panels are smaller than polycrystalline ones but still provide the same power output. This means that if you have limited roof space, investing in the more efficient monocrystalline panels can help you maximise your energy production from the area available.
Regular cleaning
By regularly cleaning and providing maintenance to your solar panels, you are also optimising their performance. When your solar panels aren’t kept clean, dust or debris accumulates, which can block out parts of your panels from receiving sunlight. Although you can clean your solar panels yourself, to reduce the safety risks, we recommend contacting our friendly team. Your panels will also need regular maintenance checks to ensure their wiring, cables, and other electrical components are performing at their maximum. These should be conducted at least every two years by a licensed solar professional.
Knowing how many solar panels can fit on your roof will help you effectively plan your new system installation. This will involve considering the factors that will impact your roof’s capacity, including its design, build condition, orientation and the effect of local regulations. To calculate how many solar panels will fit, you will require knowledge of the average panel size and your available roof space. Once you’ve determined how many panels fit, you can take measures to plan out your solar system size, in addition to steps that maximise your energy production.
Our team at TSS is prepared to help you at every stage of your solar installation. For more information, please contact our knowledgeable team here.
1300 655 808
