kW stands for kilowatts. Every gas stove burner comes with a flame rating expressed in kW. It expresses how much thermal energy the burner needs from the gas to generate a certain amount of heat for cooking. If a gas stove is rated 1 kW with 40% efficiency, it means that the stove requires 1000 joules of potential energy in 1 second to produce 0.4 kW of thermal energy. As an example, the Faber 4 Brass Burner Auto Ignition Gas Hob comes with a combination of 2.5 kW and 1.5 kW burners.