Two-Stage Products:
Traditional heating and cooling systems are designed to heat or cool your home during the coldest or hottest day in your climate. Therefore, when they are operating, they are heating or cooling at their full capacity. Two-Stage products are designed to operate like two separate systems, maintaining more consistent comfort levels throughout the home. The first stage consists of the system running at about 68% of its heating or cooling capacity. For example, a Two-Stage furnace will always start in the first stage and attempt to meet the heating demand. This reduced capacity is enough to warm a home on mild winter days. When temperatures drop, the furnace adjusts itself and enters the second stage to meet the demand within the home. The example is also true for Two-Stage cooling-with split system air conditioners and heat pumps.

Modulating Furnaces:

One of the newest developments in home furnace design, the fully modulating furnace monitors temperature and moisture conditions, and will adjust its own firing rate higher or lower as needed to maintain heating at peak efficiency for the needs of your home – so you maximize your energy efficiency while enjoying constant comfort.  The furnace operates anywhere from 15% to 100% of its capacity, based on your home’s needs. It analyzes the indoor temperature every 60 seconds and adjusts its percentage of firing accordingly.  This equipment technology, offered by RUUD, Maytag, Westinghouse, and Frigidaire, is the top of the line in heating comfort and furnace energy efficiency. 

View a presentation of the Frigidaire Modulating furnace here.

24.5-SEER - So SMART, ITS IQ DELIVERS THE HIGHEST ENERGY EFFICIENCY:
24.5-SEER IQ Drive Complete-Comfort System.  Available for the Maytag, Frigidaire, and Westinghouse product lines, the IQ Drive Air Conditioner utilizes inverter rotary technology to achieve the highest efficiency level available today. Traditional scroll compressors just turn on and off - operating at 60 hertz when running. But IQ Driver inverter technology has almost infinite modulation for a perfectly even variance. It runs as low as 15 hertz, so it uses less power. So while today's compressors kick on at full speed to compensate for a small change in temperature, IQ inverter technology alters the compressor speed just enough to match the slightest change in air temperature. So in addition to minimal power utilization, you get a more consistent temperature level - and fewer hot and cold spots.
So Quiet, You May Forget You Have It. Thanks to its impressive efficiency; the IQ Drive 24.5-SEER Comfort System delivers the lowest sound levels in the industry. Today's traditional compressors operate at 3,600-rpm power. So even with full insulation, sound blanket, sound-absorbing base, lubricated motor and swept fan blade, they make enough noise to be heard inside the home. By comparison, the IQ Drive rotary compressor can ramp down to 900 rpm for ultra-low power and ultra-low noise level. That makes for a quieter home, especially at night.

The IQ Drive System comes with the ultimate in new, quick-response features:
1. Selective Humidity Levels - Whether alone or with a humidifier, it regulates 
    the most consistent moisture levels ever.
2. Programmable Comfort Schedules - you can program a seven-day comfort schedule  
    to control up to four specific events at precise times of the day, such as wake-up 
    time, work time, home arrival or sleep time. You can even set a vacation mode for 
    ultimate energy efficiency even while you're away.
3. Filter Monitoring - Lets you know if the filter needs cleaning or replacing.
4. System Maintenance Reminders - Automatically notifies you of service intervals for 
    accessories such as electronic air cleaners, humidifiers or UV light.
5. On-Board Diagnostics - the display will let you know when any system fault is detected
    and service is needed.