Function	Pros	Cons
Economizer	Utilises the waste heat from flue gas for heating the feed water temperature	Reduces fuel consumption by 4-5%	Space taking, viable for highly functional units and also requires government regulations
Air Pre Heater	Uses the waste flue gas to heat the feed air of boiler	Reduces fuel consumption by 2-3% and lower government regulations	Requires consistent running boiler and less effective on low moisture fuel.
Solar based feed water heater	Heats feed water before entering the boiler with help of solar panels.	Faster ROI as the investment costs are low, 2-3% fuel savings.	Works only on sunny days. Thus, the operations has to be synchronized.