Think about usage, gas or electric heating, how many people use the property, how much hot water is required, how often is it needed, and will it be used at the same time, two bathrooms for example? Usage can affect the overall water supply, so you need to ensure your boiler and the heating system can cope with the demand.
Do you have any additional requirements like smart thermostats, water pumps, hot water tanks and cylinders to improve the system efficiency?
Market leaders and boiler manufacturers like Baxi, Worcester, Ideal, Bosch and Vaillant will offer extended warranties of up to ten years, so it’s important to shop around.