This is a boiler from an espresso machine that has been filled with lime buildup. It cost over $3,000.00 to correct the problem, which preventative maintenance would have prevented.
In an HVAC unit, a fan draws air across a filter. The blower has to work harder and more frequently to draw air across a dirty filter and consequently puts more strain on the parts and uses more energy. Proper filter changes and lubrication could have prevented the breakdown seen above.