An oil boiler works in a very similar way to a gas boiler. The fuel, in this case oil, is ignited in the combustion chamber and a heat exchanger warms up cold water, either from the mains in a combi system or from a cold water tank in a conventional system. The heated water can be used in your radiators, taps and showers to provide your home with heating and hot water. Oil is a more efficient fuel than gas.
The main difference between a gas and an oil boiler is the way the appliances store their fuel. A gas boiler doesn’t need to store gas because it is connected to the mains, which means it has a constant supply of fuel. In contrast, an oil boiler requires a tank to store the oil until it is needed.