Uma ukhetha izibani zasemgwaqweni, ukuphuma kwe-lumen kungenye yezindlela zobuchwepheshe ezibaluleke kakhulu okufanele uziqonde. Ama-lumen alinganisa inani eliphelele lokukhanya okubonakalayo okukhishwa umthombo wokukhanya. Ngokungafani ne-wattage, ekhombisa ukusetshenziswa kwamandla kuphela, ama-lumen abonisa ngqo ukuthi ukukhanya komgwaqo kukhanya kangakanani ngempela.