D55 Office

OnGen Case Study


OnGen Expert™ is an multi-award winning commercial assessment tool for onsite renewables and storage. It allows a user to identify energy cost and carbon savings and generate new revenue streams by assessing what renewable technologies could be deployed to a site.



OnGen developed a sophisticated Excel model to perform the calculations necessary to determine which technologies work for a given location based on a customer’s financial or carbon-saving goals. In order to scale the model, and make it available for users to self-serve, OnGen engaged us to build a web application that included the same functionality as the spreadsheet and also to enhanced it with a more complex set of user inputs such as half-hourly consumption and pricing.

OnGen is necessarily complex. In order to give an accurate view of what would happen to a site if renewable technologies were deployed, it must consider thousands of variables and perform potentially many millions of calculations.



  • D55 worked with OnGen and a University Mathematics department to find efficient algorithms. We were able to use our knowledge of the Energy Industry to help shape the functionality of the project.
  • We assisted OnGen team with how to specify software and brought our extensive knowledge of DevOps and AWS to bear so that OnGen can make changes and release easily.
  • As a start-up, running costs are important. We put in a solution that scales under load but has a low running cost in periods of inactivity.
  • SNS, SQS



OnGen Expert™ can concurrently perform many millions of calculations for a growing number of clients who can self-serve their assessments on the internet. The site scales with demand and remains responsive by offloading the calculations to services within AWS.