A proposed ordinance in Boston mandating energy audits is coming under criticism from the Greater Boston Real Estate Board and others as being too costly and intrusive. The rule would cover existing commercial buildings larger than 25,000 sf and residential buildings with 25 or more units. Owners would be required to use the EPA’s Energy Star Portfolio Manager to track their buildings’ overall energy use and that of their tenants. The information would then be converted into an energy performance rating on a scale of 1 to 100. City Hall would post the ratings online, and owners and tenants who fail to report would face fines.