The AFUE rating indicates what percentage of the energy in the fuel is converted into usable heat. If your boiler has not been well maintained, then its efficiency is further decreased. Power burners, electronic spark ignition and pulse combustion are all more efficient methods of burning the fuel. A new high efficiency boiler will incorporate one or more of these improvements. Improvements have also been made in transferring the heat of combustion to the boiler water.
Boilers lose a considerable amount of heat up the flue.
So much heat is extracted that the water vapor in the gases condenses, giving them the name condensing boilers. The exhaust gases from these type of boilers are low temperature and can be vented horizontally. There is no need for a chimney. This type of boiler would be an appropriate replacement for an electric boiler since no chimney exists. How to Proceed Contact your heating service company to do a thorough evaluation for you.