I-lembonakalo ukuba ubushushu ngu zihlolwe yi-indices ukuba ingaba kuqala ngokwendlela nge imitha ka-thermal usamuel, enxulumene amaqondo obushushu umenzi woluvo eyomileyo lobushushu bulb damp, kwaye umenzi woluvo kunye bulb encased nge zonke izigaba a iglobhu made nowekopolo. I-Ibutg kuya kubalwa ngokusekelwe i-data ezi 3 abeenzi boluvo ngolu hlobo lulandelayo: