Undertakings  will need to appoint a `Lead ESOS Assessor’ to carry out or oversee  some elements of their ESOS assessment.
The role of the Lead Assessor will vary from one undertaking to the next, as in some instance they may oversee the whole of the assessment.
However, as a minimum they should undertake the following:

• Agree sampling approach for energy assessments
• Agree the audit methodology for new assessments
• Agree what previously undertaken energy related work can be included in the evidence pack.
• Review the total energy measurement calculations
• Audit a sample No of energy assessments (where they have been undertaken by a third party)
• Review energy consumption calculations
• Review energy analysis
• Review the ESOS evidence pack and ESOS Assessments
• Compile an ESOS review report
• Sign off ESOS assessments
• Review and audit the energy assessments.
• Sign-off the assessments prior to notifying the Environmental Agency.

Finding a Lead Assessor
The Environment Agency has approved a number of professional bodies and each holds a register of energy professionals who are authorised to undertake ESOS energy assessments.

The Chartered Institute of Building Services Engineers have been given approval by DECC to hold a register which can be found at CIBSE ESOS REGISTER.