A　recent　study　proposed　an　interesting　unrelated　parallel　machines　scheduling　problem　under　time-varying　electricity　cost,　which　assumes　significant　importance　for　industrial　enterprises　competitiveness　improvement　and　sustainable　economic　development.　The　existing　solution　method　is　a　hybrid　genetic　algorithm,　which　cannot　ensure　the　optimality　of　the　solutions.　In　this　work,　we　provide　a　mixed-integer　linear　programming　model　to　exactly　solve　the　problem.　The　computational　results　show　that　the　proposed　model　can　obtain　optimal　solutions　efficiently.　©　2019　IEEE.