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Sunulator, a free solar feasibility calculator

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What is Sunulator?

Sunulator is a simulation tool that can help you plan for grid-connected solar power. Unlike most other solar calculators, Sunulator uses half-hourly consumption and generation data over a whole year to estimate how much solar generation will be consumed onsite versus exported. Based on electricity tariff information, it then calculates the impact on your electricity bill and projects the savings over a 30-year time frame. Financial results include payback period, net present value and return on investment.

We’ve used special customised versions of Sunulator in many projects for Government, energy companies and case studies.  And it has been used widely in the energy industry, including by solar installers and regulatory bodies.


Sunulator allows you to compare the results for several scenarios, e.g different sizes of solar array or panel orientations, or different amounts of battery storage.

Community investment options

In Australia most solar systems are owned directly by the electricity consumer, usually a homeowner. Sunulator can also assist community organisations to install solar systems via additional investment options:

  • A community organisation installs a system and sells electricity to the host site
  • A solar system is installed through a loan from a community organisation
  • A community organisation acts as an electricity retailer.
  • Economic returns are estimated both for investors and the host site.

You need some experience with spreadsheets and some knowledge of electricity data, e.g tariffs and kW vs kWh. You also need Microsoft Excel, version 2007 or greater, and system permissions to run macros etc.

If you find that running Sunulator yourself is problematic, we can do this for you as part of our energy advice service.


If you want to use Sunulator for locations outside the eight Australian capital cities, please download the file for your state listed below. Save it to the same place you’ve saved Sunulator, and it will automatically look into the file to find the information it needs. There are 177 locations in total; “TMY” stands for “Typical Meteorological Year”.

Regional NSW
Regional NT
Regional Queensland
Regional SA
Regional Tasmania
Regional Victoria
Regional WA

Renew has produced several  YouTube videos to introduce and help you to use Sunulator. Renew staff can also help you with Sunulator through our solar power advice service.


Is Sunulator suitable for analysing a household grid-connect solar system?
– Yes! Many householders will find Sunulator difficult to understand and use, but if you have the knowledge and time, Sunulator will do a great job.

Do I still need to get a detailed solar system design done?
– Yes! Any solar system needs to be designed to meet Australian standards, and to accommodate physical and electrical constraints. Eg strength of the roof, maximum voltage of the inverter etc.

Does Sunulator allow for site-specific conditions, e.g shading from trees?

– No. It is up to the user to be aware of such issues and apply conservative input values to allow for them. Future versions may support user-entry for shading at specific times of day and months of the year.

Why does Sunulator focus so much on economics, when environmental benefits are more important?

– Most people and organisations considering solar want to help the environment, but also have some economic criteria. The environmental benefits of a solar system are relatively simple to calculate, compared to the economics. Sunulator estimates the annual carbon dioxide avoided compared to Australian average grid electricity and presents this as a “number of cars off the road” equivalent.

Does Sunulator support batteries in a grid-connected system?

– Yes.

Can Sunulator simulate oversized arrays, where the inverter clips output at sunny times?
– No. This is on the list for future enhancement.

Can I use Sunulator for an off-grid system?
– No. The solar generation results may be informative, but Sunulator doesn’t answer important questions for offgrid systems such as battery and solar sizing to get you through several cloudy days.


Where on my electricity bill can I find the numbers to input to Sunulator?
– Unfortunately it’s not that simple. Please refer to the user guide. If you require further assistance to use Sunulator, please contact Renew.

I can enter daily and monthly profiles, but that’s not sufficently representative of my consumption pattern. What should I do?
– You may create a customised year-long consumption profile in a spreadsheet, and use the “copy and paste” function to import it to Sunulator.

What’s an appropriate value for the discount rate?

– This depends on individual circumstances. Many people choose a value related to their source of funding, or the return expected from alternative uses of their money. For more information, please see other sources e.g http://en.wikipedia.org/wiki/Discounted_cash_flow.


Why isn’t Sunulator a web-based system like Renew’s Tankulator?
– Sunulator is more complex than Tankulator. In future we would like to turn it into a web-based tool.

Can I run Sunulator in OpenOffice or other spreadsheets?
– Unfortunately not. We understand that many people prefer to use non-Microsoft products. However to meet Sunulator’s requirements for performance and functionality, we had to use Excel-specific features.

When I try to open the Sunulator file, I get “Microsoft Office Excel Security Notice” saying “Macros have been disabled”. Why is that?
– Click the button “Enable Macros”. To avoid this message in future, you can trust Sunulator’s folder in Excel’s “Trust Centre”.

When I click any button, I get a message saying macros are disabled. What’s going on?
– You need to set Excel to allow macros, and/or to trust Sunulator’s folder in Excel’s “Trust Centre”.

Excel won’t let me change the settings so that macros are allowed. What should I do?
– You may be using a computer that’s managed by someone else as the administrator. Please contact them to give you administration rights on your computer.

Why is the Excel file so big, and why does Sunulator take so long to run?
– Unlike most other solar calculators, Sunulator uses a simulation approach. Climate data is stored for a whole year in half-hourly intervals, and your consumption and tariffs are analysed the same way. Your computer hardware makes a difference – in general recent computers are much faster than older ones.

Does Sunulator work on non-English versions of Excel?
– Yes. If Sunulator does not run on your non-English software, please let us know.

Does Sunulator work on Apple computers?
– Mostly. Sunulator works on Apple computers as long as they are running a full version of Microsoft Excel 2011 or later. Excel must also have been updated, to version 14.6.1 or later. However, Microsoft didn’t give Pivot Charts to its Apple version of Excel, so some charts will not work. Also, Sunulator will not recognise supplementary files for regional locations due its different file system.


Where did you get your climate data from?
– Renew purchased satellite-based hourly insolation data from the Australian Bureau of Meteorology, from the 1990’s up to the end of 2013. Months with too much missing data were excluded. We filled gaps in the remaining data and interpolated to half-hourly values. We then prepared Typical Meteorological Year data, splicing representative months from the data set into a single composite year.

Why does Sunulator give different results from other solar calculators?
– There are several possible reasons, such as the climate data source or timeline, assumptions on solar system efficiency and economic projections. Sunulator provides several options for the user to apply different assumptions if desired.

What testing have you done to ensure that Sunulator is accurate?
– To validate Sunulator’s results, we sourced user-reported generation 2013 data from PvOutput.org for dozens of systems. Excluding those that appeared to be influenced by site-specific conditions or missing data, Sunulator’s simulation matched very well! We also validated against other solar calculators.

How can I copy results from Sunulator into another spreadsheet?
– In sheet “Stats”, just select the cells, copy them and paste into the other spreadsheet.

Can I get the detailed simulation results, e.g export vs. import by half-hour interval?
– Sunulator calculates in half-hour intervals, but does not report results at this level. Please contact Renew to discuss your requirements.

Sunulator Training 01: Consumption

Training video 1 of 7 on how to use Sunulator, Renew’s free solar feasibility calculator. To view more Sunulator training, click here.


We would like to acknowledge the help of our partners in providing this service including:

Sunulator News and Updates
Sunulator training session a success

Sunulator training session a success

Andrew Reddaway conducted workshops for solar installers at the Clean Energy Council in Melbourne on March 27 and April 9, taking the total number of training sessions held around the country to 17 since Sunulator was established in 2014.

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Sunulator in Victorian community solar first

Sunulator in Victorian community solar first

The Alternative Technology Association’s (ATA) Sunulator solar feasibility calculator has played an important part in a groundbreaking community solar project for the Geelong Sustainability Group which has been awarded $140,000 by the Victorian Government.

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