There are many variables to consider here. Probably the best approach is to do a comparison i.e. how old is the system, how often is it breaking down, are the cost of repairs mounting, is the repair cost nearing the cost of a replacement boiler? If the answer is yes to all of the above then it may be time to consider upgrading to a more efficient ‘A’ rated boiler. First, engage a professional Gas Safe Engineer to diagnose, advise and recommend the best cost-effective option.