As a boiler becomes older it loses efficiency and often becomes more unreliable. Using up more energy, an older boiler will eat into your heating costs.
The standard boiler lasts for 10-15 years. Anything longer than this amount of time and you run the risk of causing problems for yourself in the long run. According to the Sustainable Energy Authority of Ireland (SEAI) after 15 years gas boilers efficiency can drop to 60%.
With a Viessmann boiler replacement, you get much better quality and value over standard boilers. A German brand, Viessmann provide many items as part of their standard service while other manufacturers may not include these at all or at additional costs.