The phrase "Potential Impact" is used in the Recommendations Report for a Non-Domestic Energy Performance Certificate (EPC) to identify the impact carrying out each recommendation would have.  However, it is not clearly explained and often leads to confusion.  Often clients are not clear what impact is being identified (cost, carbon emissions, energy use) or how much change they can expect.
Carbon Impact
Non-domestic assessments are all based around helping the UK meet its climate obligations.  As such, they are designed to reduce carbon emissions and encourage the use of cleaner fuels.  It is therefore not surprising that the impact referred to is how much each recommended measure is likely to reduce the carbon emissions of the building.
For each recommendation that is automatically generated by the approved software, the carbon impact is automatically assessed.  An impact less than 0.5% is described as “Low”, 0.5% to 4% is described as “Medium” and greater than 4% as “High”.  For manually amended or added recommendations, the assessor should evaluate the impact using the same scale but has to do this using a modelling process.
Energy and Cost Savings
Reducing carbon emissions is not necessarily the same as reducing energy consumption or costs.  Generally, using less energy will result in lower costs and lower carbon emissions but this is not always the case.
For example, changing the fuels used could reduce carbon emissions whilst increasing costs or visa versa.  Different fuels behave differently so a cheaper fuel may have a larger carbon footprint.  Equally, consideration would need to be given to the technology and maintenance costs associated with using each fuel type.
As with any business decision, the full range of benefits and drawbacks of implementing each recommendation should be considered prior to implementation.