I need a better central A/C unit

Last winter, I noticed the furnace running for much longer cycles.  The increase in energy usage showed up on my monthly utility bill. I tried lowering the thermostat by a couple of degrees, but the house already felt a bit chilly.  The furnace was definitely putting out less air and really struggling to keep up with demand. Plus, the heated air had an unpleasant smell and was bringing dust into the home.  When my husband started coughing and complaining of a headache nearly every night, I hired a local HVAC contractor for help. The HVAC contractor checked out the furnace and found nothing beyond a minor build up of dust.  When he inspected the duct system, however, he discovered a significant accumulation of contaminants. Although I’ve been conscientious about professional upkeep for the furnace, I’d never given the ductwork a thought. Over the years, dust, construction debris, bugs, webs, and all sorts of disgusting things had settled into those pipes.  The buildup restricted the flow of air, making the furnace work much harder to achieve thermostat settings. I expected the duct cleaning process to be expensive, labor intensive and messy, Instead, the HVAC contractor brought in a piece of equipment that looked a lot like an oversized vacuum cleaner. A hose with a brush attachment fitted into the ducts to scrub and suck up the contaminants.  The process was completed in a couple of hours, with no disruption to my home and no damage to the ducts. The improvement in the operation of the furnace, comfort of the home and air quality was immediate.