OnGen and the Energy Savings Opportunity Scheme (ESOS) Phase 3

March 10, 20230

The Energy Savings Opportunity Scheme (ESOS) is a mandatory audit that organisations must carry out across their buildings every 4 years. This audit was originally introduced under the EU Energy Efficiency Directive (2012/27/EU). The original compliance date for the latest ESOS phase was 5th of December 2023, however the deadline has now been extended to 5th June 2024. OnEfficiency is a digital tool offered by OnGen is an easy way to assess the energy efficiency of a building and to suggest costed strategies than could improve an energy performance certificate (EPC) rating.  


OnGen Expert is a complementary digital service to OnEfficiency that suggests an appropriate onsite low-carbon energy generation technology system. These digital tools combine to maximise carbon reductions, lower energy costs and help contribute towards ESOS compliance. 


ESOS applies to any ‘large UK undertaking’ (roughly 11,000 in the UK) which includes businesses, not-for-profit bodies, and any other public sector organisation that: 

  • Employ 250 people or more 
  • Have an annual turnover in excess of £44 million 
  • An annual balance sheet of over £38 million 



An ESOS audit must cover 90% of the total energy usage across an organisation’s portfolio. A more detailed audit must then be carried out in order to understand where the most substantial energy savings can be made. Finally, the audit will recommend the most cost-effective energy-saving measures to implement. 

Since the last ESOS phase (ended 1 December 2019), the energy landscape has changed substantially in response to the COVID pandemic and the Ukraine war. These events have caused unprecedented volatility in the energy market, driving gas and electricity prices to record levels. 

Because of these events, more than ever, ESOS compliance should be used to an organisation’s advantage. The data collected and results from the ESOS audit can provide valuable insight for an organisation to become more energy-efficient and self-sufficient. 

OnGen offers OnEfficiency and OnGen Expert as standalone easy to access software solutions and through its Managed Service, meaning all the hard work is done for the organisation. If your company is happy with one or more of the assessed technologies, an appropriate supplier can be set up using the OnGen Marketplace where the supplier bids for your project. 

ESOS isn’t just a box-ticking exercise, it can help save money in the long term and reduce carbon emissions substantially for businesses trying to reach net zero. 

To find out more about how OnGen can help your company comply with ESOS regulations, reduce energy costs, or help to reduce your carbon emissions, get in touch today by emailing [email protected]. 

You can also access OnGen Expert directly by clicking here.

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