1.48 The Unitary Charge Escalator is applied to the Unitary Charge only. In PFI contracts, the Unitary Charge typically escalates, either wholly or in part, by reference to the Retail Price Index ("RPI"). The Spreadsheet enables Procuring Authorities to determine the extent to which the Unitary Charge is wholly or partially escalated by the OpEx (non employment) escalator. In determining what proportion of the OpEx (non employment) escalator should be used to escalate the Unitary Charge, Procuring Authorities should be guided by relevant sector-specific experience and provide, as part of their project assessment, appropriate supporting evidence.