The APVI Solar Potential Tool (SunSPoT) is an online tool for estimating the potential for electricity generation from PV on building roofs in Australian cities. The tool accounts for solar radiation and weather at the site; PV system area, tilt, orientation; and shading from nearby buildings and vegetation.

More information about the data and methodology used can be found here.

SunSPoT has been developed by the Australian PV Institute (APVI) as part of the APVI’s Solar Mapping research project, and funded by the Australian Renewable Energy Agency.

More information on this and other APVI research projects can be found here.

APVI’s Solar Map has been developed as a preliminary information tool and is no substitute to an on-site assessment performed by a certified professional. The results from the tool are only an estimate and may be inaccurate due to incomplete or out of date building models and GIS data.

Choose a city to use the tool

Shadow layer

Shadow layers displaying shadows at solar noon for the Equinox, Winter Solstice or Summer Solstice. These layers can be used to determine which surfaces will be impacted by shading at different times of the year.

Solar radiation (insolation) heat map layer

An insolation heat map displaying the average level of solar radiation (insolation) in kWh/m2/day. This layer can be used to quickly visualise the solar potential of different building surfaces. Surfaces highlighted in red provide the best options for solar. A key to the insolation heat map is shown beside the insolation slider.

How to use SunSPoT

  • Locate your building

    The map background can be switched between satellite and street view, to assist locating a building of interest. Zoom to your place of interest by double clicking on the map, or using the zoom (+/-) buttons. Manually zoom and pan to locate your specific building of interest. The maximum zoom available is zoom level 20.

  • View available data

    To visualise the data available within the map, adjust the opacity sliders (from 0 to 100%) for each of the data layers. The data layers available are listed above.

  • Identify the specific roof area for investigation

    After using the data layers to visualise your building’s solar potential, you can draw a shape over an area of interest on a single roof surface, and then simulate the annual PV output that would be expected over that area.

    Select the “Draw a polygon” or “Draw a rectangle” tool.

    • Using the “Draw a polygon” tool, click each corner of the area you wish to define. Double click the last corner to close the polygon and bring up the simulation results.
    • Using the “Draw a rectangle” tool, click and drag to draw a rectangle, releasing the mouse when you reach the opposite corner of the rectangle. This will bring up the simulation results.

    You will need to use either the insolation or a shadow layer as the background image to accurately identify building surface edges. The underlying satellite imagery contains distortions due to, for example, camera angle. The data layers are based on accurate 3D building models, which do not contain distortions and display distances accurately. Therefore offsets between the satellite imagery and the data layers exist. Use of the data layers (either insolation or shadow layers) will ensure that a shape is drawn in the correct location for simulation of PV output.

    It is important to draw your polygon/rectangle across a single roof surface. Polygon/rectangles drawn across multiple surfaces will lead to inaccurate calculations. Each surface of a building will need to be investigated separately.

  • Review the results for your identified area

    After drawing your area of interest, the results panel will appear on the right-hand side of your screen. The panel will by default display the results for a flush mounted PV system (which is mounted in parallel to the roof surface, with an air gap of approximately 10 cm between the PV panels and the roof). You can switch to a rack-mounted PV system at an alternative tilt and orientation.

    The simulation results include:

    • Approximate Area: The approximate area in m2 of the drawn polygon/rectangle
    • Insolation: The average level of solar radiation (insolation in kWh/m2/day) available at the surface within the identified area
    • Orientation: The average orientation of the surface within the identified area
    • Tilt: The average tilt angle of the surface within the identified area
    • System Size: The estimated photovoltaic (PV) system size in kW that can be installed on the surface within the identified area. System size will change when a new roof area is selected, which fits a different number of panel; and also when rack or flush mounting, or different tilt and orientation options are used on the same roof area, as the spacing between panels changes to avoid self shading.
    • AC power output: The estimated monthly and annual AC energy output in kWh of the PV system. This can be compared to the energy consumption in kWh of the building by reviewing the relevant electricity bills.
    • Annual output per kW of installed capacity: The estimated annual output from the PV system per KW of installed capacity in kWh/kW. This can be used to compare the performance of PV systems mounted at different locations or tilt/orientation angles.
    • Estimated Annual Saving: The estimated annual financial savings in $ per annum, assuming the electricity price in the box. This is calculated by multiplying the kWh generated annually by the electricity price in c/kWh. You can adjust the electricity price in order to assess the value of electricity generated by the PV system when it is used to offset retail electricity prices, which are typically 20-30 c/kWh for residential customers and 12-25 c/kWh for commercial customers in Australian cities. Alternatively, you may enter the price that a retailer might offer for PV electricity exported at times when the PV generation exceeds the load. This may be from 0 to 60 c/kWh, depending on the retailer and the availability of premium feed-in tariffs.
    • CO2 offset: The estimated annual carbon emissions savings in tonnes of CO2 per annum, based on the average emissions from grid electricity in the relevant state or territory, and considering emissions created during the manufacture of the PV system.

    You have the ability to adjust both the calculated System size in kW and the price of electricity in cents per kWh.

    It is difficult to estimate the financial savings that could result from the installation of a PV system. Financial savings will be dependent on the electricity tariffs that your energy retailer offers, in addition to the amount of energy you import from or export to the electricity grid, which is dependent on the time of day that you use electricity.

  • Define a rack mounted PV system

    For roof surfaces with tilt angles below 15°, the user has the ability to investigate the output from a rack mounted PV system. To utilise this option click on the “Rack mounted” option and adjust the “Orientation” and “Tilt” slide bars to the angles you wish to investigate. The calculations will update automatically with each adjustment of the slide bars.

    Please note:

    • This option is not available if the user drawn polygon/rectangle was drawn on a roof with a tilt angle greater than 15°, which would not be suitable for rack mounting.
    • Rack mounted systems are typically orientated by a multiple of 90 degrees (i.e. 0, 90, -90 or 180 degrees) from the roof surface orientation. This practice occurs to minimise the cost of installation.
    • The rack mounted option assumes that the PV system is mounted in consecutive rows of PV modules. The calculation of the PV system size takes into consideration the spacing required between the rows to avoid self-shading of the PV modules (where the PV modules in front shade those behind). The calculation avoids shading based on the position of the sun between 9am and 3pm on the winter solstice for PV system orientated roughly north and between 7am and 5pm on the summer solstice for PV systems orientated roughly south. This ensures that any self-shading would have a minimal impact on the output of the PV system. It may be economic or desirable to install PV panels closer together and accept higher losses due to shading, particularly on roofs where the area available to install a PV system is limited.

About the calculations

SunSPoT uses 3D building and vegetation models from AAM and Typical Meteorological Year (TMY) weather data from the US Department of Energy Simulation Software Weather Data webpage to calculate average annual and monthly incident solar radiation on a building surface and the expected performance of a typical PV system of the size specified by the user, with PV panel orientation and tilt defaulting to that of the roof surface, or defined by the user.

The tool accounts for solar radiation and other weather variables at the site, and shading impacts of surrounding buildings and vegetation. Detailed information about the data and methodology used in SunSPoT can be found here.


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