A new report from a prominent business group has found that the cost to consumers of New York City Mayor Bill de Blasio’s proposal to ban natural gas hookups in new buildings by 2030 could be “astronomical.”

The report by the Consumer Energy Alliance (CEA), whose membership includes hundreds of businesses and business groups including BP plc, Enbridge Inc. and ExxonMobil, found that the ban could cost every household at least $25,600. 

“Mayor de Blasio’s natural gas service ban is nothing short of ill-conceived and irresponsible,” said CEA’s Wendy Hijos, New York director. “It will be acutely felt by the poor and those on fixed incomes who disproportionately struggle with higher energy bills and disruptions.”

The CEA report details how the energy ban would...