Boiler installations can take up to anywhere between a day to a few days depending on the manner of the installation. If you are getting a like-for-like swap of your current boiler, this will be less time consuming for the installer and they should be able to complete the job in around 2-4 hours. However, if you’re changing your system completely, e.g. from a system boiler to a combi boiler, this will take much longer to complete due to several external factors from the boiler, including pipework and removing your hot water cylinder.
When the ECO-Heat installer suggests a suitable boiler for your property, they should be able to give you a more accurate installation timescale.