As Kyle mentioned above, reporting in "detailed" frequency would tell us more what is happening at system time step. So Output:Variable, should have detailed frequency instead of hourly or timestep. Also, how Air System Total Heating Energy and Air System Total Cooling Energy are calculated in EnergyPlus is described below. Reporting each of these outputs should answer the question.

SysTotHTNG = SysFANCompHTNG+ SysHCCompHTNG+ SysHeatExHTNG+ SysHumidHTNG+ SysSolarCollectHeating+ SysUserDefinedTerminalHeating;

SysTotCLNG = SysCCCompCLNG+ SysHeatExCLNG+ SysEvapCLNG+ DesDehumidCLNG+ SysSolarCollectCooling+ SysUserDefinedTerminalCooling;

SysTotHTNG : "Air System Total Heating Energy [J]"
SysTotCLNG : "Air System Total Cooling Energy [J]"

SysFANCompHTNG : "Air System Fan Air Heating Energy [J]"
SysHCCompHTNG : "Air System Heating Coil Total Heating Energy [J]"
SysHeatExHTNG : "Air System Heat Exchanger Total Heating Energy [J]"
SysHeatExCLNG : "Air System Heat Exchanger Total Cooling Energy [J]"
SysSolarCollectHeating : "Air System Solar Collector Total Heating Energy [J]"
SysSolarCollectCooling : "Air System Solar Collector Total Cooling Energy [J]"
SysUserDefinedTerminalHeating : "Air System User Defined Air Terminal Total Heating Energy [J]"
SysUserDefinedTerminalCooling : "Air System User Defined Air Terminal Total Cooling Energy [J]"
SysHumidHTNG : "Air System Humidifier Total Heating Energy [J]" 
DesDehumidCLNG : "Air System Desiccant Dehumidifier Total Cooling Energy [J]"

As Kyle mentioned above, reporting in "detailed" frequency would tell us more what is happening at system time step. So Output:Variable, should have detailed frequency instead of hourly or timestep. Also, how Air System Total Heating Energy and Air System Total Cooling Energy are calculated in EnergyPlus is described below. Reporting each of these outputs should answer the question.

SysTotHTNG = SysFANCompHTNG+ SysHCCompHTNG+ SysHeatExHTNG+ SysHumidHTNG+ SysSolarCollectHeating+ SysUserDefinedTerminalHeating;

SysTotCLNG = SysCCCompCLNG+ SysHeatExCLNG+ SysEvapCLNG+ DesDehumidCLNG+ SysSolarCollectCooling+ SysUserDefinedTerminalCooling;

SysTotHTNG : "Air System "AirSystem Total Heating Energy [J]"
SysTotCLNG : "Air System "AirSystem Total Cooling Energy [J]"

SysFANCompHTNG : "Air System "AirSystem Fan Air Heating Energy [J]"
SysHCCompHTNG : "Air System "AirSystem Heating Coil Total Heating Energy [J]"
SysHeatExHTNG : "Air System "AirSystem Heat Exchanger Total Heating Energy [J]"
SysHeatExCLNG : "Air System "AirSystem Heat Exchanger Total Cooling Energy [J]"
SysSolarCollectHeating : "Air System "AirSystem Solar Collector Total Heating Energy [J]"
SysSolarCollectCooling : "Air System "AirSystem Solar Collector Total Cooling Energy [J]"
SysUserDefinedTerminalHeating : "Air System "AirSystem User Defined Air Terminal Total Heating Energy [J]"
SysUserDefinedTerminalCooling : "Air System "AirSystem User Defined Air Terminal Total Cooling Energy [J]"