In most cases, a boiler can be installed in a single day - especially when you use the right boiler installation company. The system as a whole? That can take a little longer. When you are looking for a boiler to be installed, you might find that the property might be without heating and hot water until the whole system is complete. The heating systems in the boiler - including the pipes, storage vessels, valves, controls, and electrical connections - can take longer to install.