Today, we pretty much take home comfort for granted. But we haven't always been so fortunate. In fact, compared to even the most basic of today's systems, the home comfort equipment of even a few decades ago seems almost primitive.

Controls.

Early thermostats were mechanical in nature, regulating system operation using either mercury or a metal strip that would expand or contract with the ambient temperature to open and close a switch. Today, sophisticated electronic sensors use varying electrical resistance to sense temperature, anticipating heating and cooling needs before you even know you're uncomfortable. Some, like the iComfort Wi-Fi^® touchscreen thermostat, can hold the temperature in your home to within .5 degree or less of your set temperature.

Airflow.

Furnaces used to operate at only one speed. They'd wait until the home was too cold, then blast it with warm air until it was too hot. Then repeat the cycle over and over. Today's furnaces, like the Lennox^® SLP98V, offer variable-speed airflow that changes based on demand, ramping up and down as needed to keep a quiet, even flow of air moving through the home. This also means quieter startups, and no startling rush of hot air. See variable-speed airflow here.

Heating.

Furnaces have always used fire in some capacity. But the way they use it has changed quite a bit. Conventional furnaces use a series of burners that warm the air as it passes through the furnace. They come on when heat is needed, and go off when it isn't. More sophisticated furnaces like the high-efficiency EL296V can burn fuel at different rates to produce varying amounts of heat based on demand. This helps it operate much more efficiently than a single-stage furnace.

Some furnaces, like the SLP99V with Precise Comfort^® technology, can adjust output in increments of as little as 1% for pinpoint comfort and amazing efficiency.

Cooling.

Like conventional furnaces, conventional air conditioners and heat pumps operate at one speed. They cool when it's hot inside, and they shut off when it isn't.

Today's most modern air conditioners and heat pumps, like the XC25 and XP25, can adjust compressor speed to many different levels, like a dimmer switch. This makes them incredibly efficient, with the added benefit of extremely quiet operation.