Thinking about replacing your boiler? The time it takes to fit a new one depends on the type of boiler you choose and the complexity of the installation. A like-for-like replacement can usually be completed in a day, while more complex jobs—such as moving the boiler to a new location or switching from a system to a combi boiler—can take two to three days. A professional installer will be able to give you a more accurate timescale after assessing your home and heating needs.