@Yan, I think you are right, looking at the code, it seems I may not have been able to directly enter therms for "The Conversion Factor Choice; so I convert from dollars/therm to dollars/kBtu within the measure. So the unit in the measure argument should be "$/therm". I'll review this, fix and push an update to BCL. Below is the relevant code. It affects both district heating and cooling. Thanks for pointing this out!

# distclg tariff object
if args['distclg_rate'] > 0
  new_object_string = "
  UtilityCost:Tariff,
    DistrictCooling Tariff,                             !- Name
    DistrictCooling:Facility,                           !- Output Meter Name
    KBtu,                                  !- Conversion Factor Choice
    ,                                       !- Energy Conversion Factor
    ,                                       !- Demand Conversion Factor
    ,                                       !- Time of Use Period Schedule Name
    ,                                       !- Season Schedule Name
    ,                                       !- Month Schedule Name
    Day,                                    !- Demand Window Length
    0.0;                                    !- Monthly Charge or Variable Name
    "
  distclg_tariff = workspace.addObject(OpenStudio::IdfObject::load(new_object_string).get).get

  # make UtilityCost:Charge:Simple objects for distclg
  #value = OpenStudio::convert(args['gas_rate'],"1/therms","1/Kbtu").get # todo - get conversion working
  value = args['distclg_rate']/99.98 # $/therm to $/Kbtu
  new_object_string = "
  UtilityCost:Charge:Simple,
    DistrictCoolingTariffEnergyCharge, !- Name
    DistrictCooling Tariff,                             !- Tariff Name
    totalEnergy,                            !- Source Variable
    Annual,                                 !- Season
    EnergyCharges,                          !- Category Variable Name
    #{value};          !- Cost per Unit Value or Variable Name
  "
  distclg_utility_cost = workspace.addObject(OpenStudio::IdfObject::load(new_object_string).get).get
end