The greenstar i with installation costs around £, and the boiler alone varies in price from £ it is always advisable to use an installed price when comparing boiler prices, unless you have someone qualified to carry out the installation for you. The staff at monkey wrench is a friendly bunch that are here to make your life easier! If you schedule an appointment during this time our fee is $. per hour, plus any parts needed, with a one hour minimum. Efficiency labels for.