The deadline for compliance with Phase 3 of the Energy Savings Opportunity Scheme (ESOS) is just a few months away. If your organisation does not already have a lead assessor in place, now is the time to secure one. Here’s what you need to know.

Compulsory for compliance

Having a lead assessor for your ESOS compliance is not optional; it is compulsory. The official ESOS guidance says that all businesses in scope of ESOS are obliged to recruit a lead assessor to review their energy audits and ESOS reporting.        

The only exception would be if your business has secured ISO 50001 certification as its route to ESOS compliance. But, as we explain in our blogpost on ISO 50001, this is a more challenging route than the conventional one and definitely not an easy way to avoid the need for a lead assessor.

Finding your ESOS lead assessor

There are a number of registers of approved ESOS lead assessors, provided by professional bodies. Any organisation wanting to appoint a lead assessor must choose one who is on one of these registers. The full list of approved registers is provided in the ESOS official guidance. When choosing a lead assessor you should direct any questions to the professional body whose register they are listed on.

If you already have a qualified ESOS lead assessor in-house, it is absolutely fine to use them for your ESOS assessment. But they do still have to be a member of an approved register.

Questions to consider

If you recruit an external ESOS lead assessor, you need to think about how big you want their role to be. There are basically two choices:

  • Get your ESOS lead assessor to do the entire audit themselves; or
  • Do the ESOS audit in-house and get the lead assessor to sign it off.

Your decision will depend on how much in-house expertise and resourcing you have.

Whoever carries it out, your ESOS assessment will identify multiple possibilities for energy-saving measures – that is the whole point of ESOS, after all. So another question to consider is whether you want the assessor to help your organisation implement the selected measures. We recommend selecting an ESOS lead assessor who is capable of this, so you can get started as soon as possible with saving your business energy and money.

When selecting your ESOS lead assessor, it is a good idea to ask prospective candidates:

  • How much experience do they have in your sector?
  • Can they provide examples of work they have done with similar businesses?
  • Are they qualified to help you implement the measures suggested in your ESOS assessment, or can they connect you with others who can?

Next steps

With the compliance deadline approaching fast, securing the best possible ESOS lead assessor should be the next priority for your organisation.

At the time of writing (February 2024), the IT system for submitting ESOS compliance notifications is still in development, but you can now register for an account. Your organisation should already have received a link to the online form, which requires information including the name of your lead assessor. If you have not received this link and believe your organisation is in scope for ESOS Phase 3, contact the Environment Agency (ESOS scheme administrators) on

Speak to Sustainable Energy First about securing an ESOS lead assessor. Complete the form to get in touch.