General description The Comet Electric Combination Boiler provides the comfort and convenience of wet central heating and domestic hot water for properties without access to mains gas. This fully controllable packaged unit is designed for 24/7 operation and is housed in an elegant enclosure. It is available in three output options: 9kW, 12kW, or 14.4kW, and includes a 140 Litre Duplex Stainless Steel Hot Water Cylinder.